Systems and methods for providing an asymmetrical tibial component

ABSTRACT

Systems and methods for providing deeper knee flexion capabilities. In some instances, such systems and methods include a tibial component that has an asymmetrical articular plateau that includes a medial tibial condylar surface and a lateral tibial condylar surface. In some cases, at least one of the medial condylar surface and the lateral condylar surface includes a concave articulation surface having a lowest point that disposed from a posterior edge of the tibial component by between about 18% and less than about 35% of a total anteroposterior dimension of the tibial component. Other implementations are also discussed.

RELATED APPLICATIONS

This is a continuation application that claims priority to U.S. patentapplication Ser. No. 14/270,041, filed May 5, 2014, and entitled SYSTEMSAND METHODS FOR PROVIDING AN ASYMMETRICAL TIBIAL COMPONENT, which is acontinuation application that claims priority to U.S. patent applicationSer. No. 13/831,352, filed Mar. 14, 2013, and entitled SYSTEMS ANDMETHODS FOR PROVIDING AN ASYMMETRICAL TIBIAL COMPONENT (now U.S. Pat.No. 8,715,360), which is a continuation application that claims priorityto U.S. patent application Ser. No. 13/802,596, filed Mar. 13, 2013, andentitled SYSTEMS AND METHODS FOR PROVIDING A FEMORAL COMPONENT (now U.S.Pat. No. 9,107,769), which is a continuation-in-part application of U.S.patent application Ser. No. 13/758,855, filed Feb. 4, 2013, and entitledSYSTEMS AND METHODS FOR PROVIDING STEM ON A TIBIAL COMPONENT (now U.S.Pat. No. 9,101,478), which is a continuation application of U.S. patentapplication Ser. No. 12/797,372, filed Jun. 9, 2010, and entitledSYSTEMS AND METHODS FOR PROVIDING DEEPER KNEE FLEXION CAPABILITIES FORKNEE PROSTHESIS PATIENTS (now U.S. Pat. No. 8,366,783), which is acontinuation-in-part of U.S. patent application Ser. No. 12/482,280,filed Jun. 10, 2009, and entitled SYSTEMS AND METHODS FOR PROVIDINGDEEPER KNEE FLEXION CAPABILITIES FOR KNEE PROSTHESIS PATIENTS (now U.S.Pat. No. 8,382,846), which is a continuation-in-part of U.S. patentapplication Ser. No. 12/198,001, filed Aug. 25, 2008, and entitledSYSTEMS AND METHODS FOR PROVIDING DEEPER KNEE FLEXION CAPABILITIES FORKNEE PROSTHESIS PATIENTS (now U.S. Pat. No. 8,273,133), which claimspriority to U.S. Provisional Patent Application Ser. No. 60/968,246,filed Aug. 27, 2007, and entitled SYSTEMS AND METHODS FOR PROVIDINGDEEPER KNEE FLEXION CAPABILITIES FOR KNEE PROSTHESIS PATIENTS, and toU.S. Provisional Patent Application Ser. No. 60/972,191, filed Sep. 13,2007, and entitled SYSTEMS AND METHODS FOR PROVIDING DEEPER KNEE FLEXIONCAPABILITIES FOR KNEE PROSTHESIS PATIENTS, each of which is incorporatedherein in its entirety by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to knee prostheses. In particular, thepresent invention relates to systems and methods for providing deeperknee flexion, or full functional flexion capabilities, more physiologicload bearing and improved patellar tracking for knee prosthesispatients. Specifically, these improvements include one or more of thefollowing: (i) adding more articular surface to the antero-proximalposterior condyles of a femoral component, including methods to achievethat result, (ii) modifications to the internal geometry of the femoralcomponent and the associated femoral bone cuts with methods ofimplantation, (iii) asymmetrical tibial components that have an uniquearticular surface that allows for deeper knee flexion than haspreviously been available, (iv) asymmetrical femoral condyles thatresult in more physiologic loading of the joint and improved patellartracking, and (v) resection of essentially all of the anterior femoralarticular cartilage and underlying bone, but no additional bone andreplacing it with a femoral component that does not have an anteriorflange as seen on contemporary prostheses.

2. Background and Related Art

Orthopedic surgeons are experiencing a proliferation of knee replacementsurgeries. The demand appears driven by the fact that few proceduresreturn as much quality of life as joint replacement.

Moreover, the increased need for knee replacements implicates the needfor durable and long lasting artificial knee devices that provide forand allow full, functional flexion. That is, there is a great need forresearch that provides new medical advances on the overall function andperformance of knee prostheses, and improves corresponding surgicalmaterials and technologies related to such devices.

Improvements to knee prostheses correspondingly increase with demand.Thus, currently-available knee prostheses mimic characteristics of thenormal knee more than those previously used. Unfortunately, today's kneeprostheses still have many shortcomings.

Among the shortcomings is the inability of a knee prosthesis patient toachieve deep knee flexion, also known as full functional flexion. Thoughsome currently available knee prostheses allow for knee flexion (i.e.,bending) of more than 130 degrees from full limb extension (zero degreesbeing when the patient's knee is fully extended and straight); some suchprostheses do not allow patients to flex from full extension to 160degrees and beyond. Full functional or deep knee flexion is where thelimb is bent to its maximum extent, which may be with the femur andtibia at an angle to each other of 140 degrees or more, though theactual angle varies from person to person and with body habitus. Fullextension is where the leg/limb is straight and the person is in astanding position.

To illustrate the average range in degrees achieved by patients havingstandard knee prostheses, the following is provided. When a patient'sknee or limb is fully extended, the femur and tibia are in the sameplane at zero degrees, or up to 5-10 degrees of hyperextension in someindividuals. However, once the knee bends, and the distal tibia movestoward the buttocks, the angle increases from zero to 90 degrees for aperson sitting in a chair. Furthermore, when the tibia is closest to thefemur, and the heel is almost at, if not touching, the buttock, theangle is around 160 degrees or more. Most conventional knee prosthesispatients are unable to consistently achieve the latter position or anyposition placing the knee joint at angles above 130 degrees (e.g., at160 degrees and beyond).

For many people, such a limb and body position is not often achieved ordesired most of the time. However, nearly everyone, at some point intime, whether or not it occurs when a person is getting on and off theground to play with children, or merely incidental to those livingactive lifestyles, finds themselves in a position requiring knee flexiongreater than 130 degrees. Unfortunately, those with currently-availableknee prostheses are unable to participate in any activity requiringgreater knee flexion and are thus limited to watching from thesidelines.

In many populations and cultures such a limb/knee and body position isdesired and necessary the majority of the time. For instance, in Asianand Indian cultures, full functional flexion and the squatting positionis common and performed for relatively long periods of time.

A need, therefore, exists for knee prostheses for those patients andespecially for those in cultures where extensive squatting, sitting withknees fully flexed, and/or kneeling when praying or eating is common, toachieve knee flexion greater than presently possible among those whohave currently-available knee prostheses.

Thus, while techniques currently exist that relate to knee prostheses,challenges still exist. Accordingly, it would be an improvement in theart to augment or even replace current techniques with other techniques.

SUMMARY OF THE INVENTION

The present invention relates to knee prostheses. In particular, thepresent invention relates to systems and methods for providing deeperknee flexion capabilities for knee prosthesis patients, and moreparticularly by effectuating one or more of the following: (i) providinga greater articular surface area to the femoral component of a kneeprosthesis, with either a modification of, or an attachment to thefemoral component of a knee prosthesis, which when integrated with apatient's femur and an appropriate tibial component, results in fullfunctional flexion; (ii) providing modifications to the internalgeometry of the femoral component and the opposing femoral bone withmethods of implanting; (iii) providing asymmetrical under surfaces onthe tibial component of the knee prosthesis and uniquely-positionedarticular surfaces to facilitate full functional flexion; (iv)asymmetrical femoral condylar surfaces with a lateralized patellar(trochlear) groove to more closely replicate physiologic loading of theknee and to provide better tracking of the patella; and (v) resection ofessentially all of the anterior femoral articular cartilage andunderlying bone, but no additional bone and replacing it with a femoralcomponent that does not have an anterior flange as seen on contemporaryprostheses.

In a normal knee, there is a cessation of active flexion atapproximately 120°, first, because the hamstring muscles lose theirmechanical advantage, and secondly because the medial femoral condylerolls posteriorly which does not occur up to 120°. By 120° of flexion,the medial femoral condyle starts to roll backwards relative to theposterior horn of the medial meniscus of the tibia. At 140° of flexion,the femur moves up on to the posterior horn of the medial meniscus.Accordingly, resistance to flexion is felt at this point and beyond. Byfull flexion, the medial femoral condyle has moved back approximately 8mm from its position at 120° to a position 10 mm from the posteriortibial cortex. Laterally, the femur moves back an additional 5 mm inhyperflexion so that there is little or no tibiofemoral rotation between120° and 160°. Accordingly, the hyperflexion between 120° and 160° is aseparate arc than the kinematics from 0° to 120° of flexion, and at160°, the posterior horn of the lateral meniscus comes to lie on theposterior surface of the tibia distal to the femoral condyle. As such,the posterior horn is not compressed and the two bones are in directcontact.

The final limit to hyperflexion arises because the posterior horn of themedial meniscus impedes flexion at 140° and limits it absolutely at160°. The posterior horn also prevents the medial femoral condyle frommoving back beyond a point 10 mm from the posterior tibial cortex. Thus,the posterior horn of the medial meniscus is a key structure inachieving deep flexion.

Implementation of the present invention takes place in association withimproved knee prostheses that enable knee prosthesis patients to achievegreater deep knee flexion than previously achievable usingpresently-designed knee prostheses. In at least some implementations ofthe present invention, greater deep knee flexion is provided to the kneeprosthesis by resecting portions of the femur to allow additionalclearance for the posterior horn of the medial meniscus and the tibia.In other implementations in which a portion of the tibia is replaced bya prosthesis, however, the posterior horn is left intact. Additionally,at least some implementations of the present invention further providepositioning and/or installing an articular surface within resectionedportions of the femur to provide an interface between the posterior hornof the medial meniscus and the resectioned surface of the femur.

In at least some implementations of the present invention, greater deepknee flexion is provided to the knee prosthesis by providing anarticular surface on the proximal, anterior surface (or portion) of theposterior condyles of the femur. At least some implementations of thepresent invention embrace an additional or increased articular surfaceon the proximal, anterior portion of either or both of the medial orlateral posterior condyles of the femoral component of the prosthesis.Embodiments of the femoral component add increased articular surfacearea to the proximal end of the posterior condyles of the femoralcomponent in an anterior direction such that when the patient bends hisor her knee during deep knee flexion, contact between the femoralcomponent and the tibial component is maintained, and a greater, deeperknee flexion can be achieved.

In at least some implementations of the present invention, greater deepknee flexion can be provided or improved by modifying the tibialarticulation, in which the center of the conforming medial tibialarticular surface of the tibial component of the prosthesis is movedposterior relative to what is currently available. Additionally, in somesuch embodiments, the overall shape of the lateral tibial articularsurface is modified.

In at least some implementations of the present invention, greater deepknee flexion can be achieved by providing an asymmetrical femoralcomponent of the prosthesis. The asymmetrical femoral component permitstransfer of more than one-half of the force transmitted across the jointto be transmitted to the medial side, as occurs in the normal knee. Insome implementations, other modifications to the tibial and femoralcomponents of a knee prosthesis may be made, including having asymmetricfemoral condyles, having a closing radius on the femoral component, andremoving certain areas of the tibial and femoral components; wherein allof the foregoing result in deeper knee flexion capabilities for kneeprosthesis patients than previously achievable.

At least some implementations of the present invention include a femoralcomponent (and associated methods for making and using such a component)that includes a femoral articular surface extending in an anteriordirection from a proximal end of a posterior condyle of a femoral kneereplacement component, the femoral component further having a fullanterior articular extension which replaces the anterior articularcartilage of a femur. In some cases, the femoral component includes afirst interior surface and a second interior surface that runsubstantially parallel to each other. In other cases, the first interiorsurface and the second interior surface of the femoral component divergefrom each other less than a 45° angle. In some instances, the firstinterior surface and the second interior surface diverge from each otherby an angle between approximately 3° and approximately 10°.

While the methods, modifications and components of the present inventionhave proven to be particularly useful in the area of knee prostheses,those skilled in the art will appreciate that the methods, modificationsand components can be used in a variety of different orthopedic andmedical applications.

These and other features and advantages of the present invention will beset forth or will become more fully apparent in the description thatfollows and in the appended claims. The features and advantages may berealized and obtained by means of the instruments and combinationsparticularly pointed out in the appended claims. Furthermore, thefeatures and advantages of the invention may be learned by the practiceof the invention or will be obvious from the description, as set forthhereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the manner in which the above recited and other featuresand advantages of the present invention are obtained, a more particulardescription of the invention will be rendered by reference to specificembodiments thereof, which are illustrated in the appended drawings.Understanding that the drawings depict only typical embodiments of thepresent invention and are not, therefore, to be considered as limitingthe scope of the invention, the present invention will be described andexplained with additional specificity and detail through the use of theaccompanying drawings in which:

FIGS. 1A and 1B depict ranges of flexion of a knee joint;

FIGS. 2A-2C and 3A-3C depict various views of a generic knee prosthesis;

FIGS. 4A-4D depict representative perspective views of embodiments of afemoral component of a knee prosthesis in accordance with embodiments ofthe present invention;

FIGS. 5A-5D depict representative perspective views of embodiments of afemoral component of a knee prosthesis in accordance with embodiments ofthe present invention;

FIGS. 6A-6B depict side views of a representative prior art tibialcomponent of a knee prosthesis;

FIGS. 6C-6D depict side views of a representative embodiment of a tibialcomponent in accordance with embodiments of the present invention;

FIGS. 6E-6F depict an alternate embodiment of a representative tibialcomponent modified to include a raised ridge articulation feature;

FIGS. 6G-6H depict an alternate embodiment of a representative tibialcomponent modified to include a spherical articulation feature;

FIG. 6I illustrates an alternate embodiment of a representative tibialcomponent modified to include the raised ridge articulation feature;

FIGS. 6J and 6K depict side views of a representative embodiment of atibial component in accordance with embodiments of the presentinvention;

FIGS. 7A and 7B depict alternate embodiments of femoral and tibialcomponents in accordance with embodiments of the present invention;

FIG. 8A illustrates a conventional femoral component while FIG. 8Billustrates an embodiment of a femoral component in accordance with thepresent invention;

FIG. 9 illustrates a modular attachment for use with embodiments of afemoral component in accordance with embodiments of the presentinvention;

FIGS. 10A-10H illustrate representative steps for attaching anembodiment of a femoral component to a femur, the resectioned portionsof the femur shown in phantom;

FIGS. 11A-11K illustrate representative steps for attaching an alternateembodiment of a femoral component to a femur;

FIGS. 12A-12C and FIG. 13 illustrate comparisons between a conventionalfemoral component and some embodiments of a femoral component inaccordance with embodiments of the present invention;

FIG. 14 illustrates an alternate embodiment of a femoral component inaccordance with embodiments of the present invention;

FIGS. 15A-15E illustrate comparisons between embodiments of a femoralcomponent;

FIGS. 16A-16D illustrate a manner in which an articulating surface ofthe femoral components shown in FIGS. 15A-15D may be extended;

FIG. 16E illustrates a shortened embodiment in which an articulatingsurface of the femoral component may be extended;

FIGS. 16F-16P illustrate flexion of a non-limiting embodiment of afemoral component having a decreasing radius, wherein the decreasingradius provides laxity over a portion of the range of flexion inaccordance with a representative embodiment of the present invention;

FIG. 16Q illustrates a unicompartmental femoral component including anextended articulating surface in accordance with a representativeembodiment of the present invention;

FIG. 16R illustrates a unicompartmental femoral component including adecreasing radius and an indentation in accordance with a representativeembodiment of the present invention;

FIG. 16S illustrates a truncated femoral component including anindentation in accordance with a representative embodiment of thepresent invention;

FIG. 16T illustrates a cross-section view of a femoral component coupledto a modular patella-femoral component in accordance with arepresentative embodiment of the present invention;

FIG. 16U illustrates a cross-section view of a femoral componentslidably coupled to a modular patella-femoral component in accordancewith a representative embodiment of the present invention;

FIG. 16V illustrates a detailed cross-section view of a femoralcomponent having a tapered opening adjustably and slidably coupled to apost of a modular patella-femoral component in accordance with arepresentative embodiment of the present invention;

FIG. 16W illustrates a cross-section view of a femoral component havinga convex surface abutted with a concave surface of a modularpatella-femoral component in accordance with a representative embodimentof the present invention;

FIGS. 16X-16Z illustrate flexion of a non-limiting embodiment of afemoral component having femoral full flexion articulation in accordancewith a representative embodiment of the present invention;

FIG. 17 illustrates drawing of a radiograph of a normal knee flexed toapproximately 160 degrees, and further illustrating the position of thepatella;

FIGS. 18A through 18C illustrate alternate embodiments of a femoralcomponent in accordance with representative embodiments of the presentinvention;

FIG. 19A illustrates a tibial component that does not have an articularsurface posterior to the main articular surface;

FIG. 19B illustrates the tibial full flex articulation being posteriorto the main weight bearing articulation;

FIGS. 20A-20I illustrate a representative interaction of a femoral fullflex articulation and a tibial full flex articulation;

FIG. 21 illustrates a representative interaction of the posteriorarticulate surface of the medial plateau of the tibia and the poplitealsurface during deep flexion of the knee;

FIG. 22 illustrates a representative implementation of a resection blockand the femur following resection of the popliteal surface;

FIG. 22A illustrates a representative implementation of a resectionblock and the femur prior to resection of the popliteal surface;

FIG. 23 illustrates a representative interaction of the posteriorarticular surface of the medial plateau of the tibia and an extendedportion of the femoral component of the knee prosthesis during deepflexion;

FIG. 23A illustrates a representative interaction of the posterior fullflex articular surface of the medial tibial plateau of a tibialcomponent and an extended portion of the femoral component of the kneeprosthesis during deep flexion;

FIG. 24 illustrates a cross-section view of a tibial component and steminserted within a tibia in accordance with a representative embodimentof the present invention;

FIGS. 25-27 illustrate various embodiments of stems in accordance withrepresentative embodiments of the present invention;

FIG. 28A illustrates an adjustable stem in accordance with arepresentative embodiment of the present invention;

FIG. 28B illustrates a tibial component comprising a modular stem inaccordance with a representative embodiment of the present invention;and

FIGS. 29A-29C each illustrate a different representative embodiment ofan implanted femoral component having two opposing internal surfacesthat run substantially parallel to each other.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to knee prostheses. In particular, thepresent invention relates to systems and methods for providing deeperknee flexion capabilities for knee prosthesis patients, and moreparticularly, to: (i) providing an extended articular surface on theproximal, anterior surface (or portion) of the posterior condyles of thefemur; (ii) making modifications to the internal geometry of the femoralcomponent and the associated femoral bone cuts with methods ofimplantation; (iii) making modifications to the tibial and femoralcomponents of a knee prosthesis, including asymmetrical tibial articularsurfaces and removing certain areas of the tibial and femoralcomponents; (iv) having asymmetric femoral condyles, including theoption of having a closing radius on the femoral component, wherein allof the foregoing result in deeper knee flexion capabilities for kneeprosthesis patients than previously achievable; and (v) resection ofessentially all of the anterior femoral articular cartilage andunderlying bone, but no additional bone and replacing it with a femoralcomponent that does not have an anterior flange as seen on contemporaryprostheses.

It is emphasized that the present invention, as illustrated in thefigures and description herein, may be embodied in other forms. Thus,neither the drawings nor the following more detailed description of thevarious embodiments of the system and method of the present inventionlimit the scope of the invention. The drawings and detailed descriptionare merely representative of examples of embodiments of the invention;the substantive scope of the present invention is limited only by theappended claims recited to describe the many embodiments. The variousembodiments of the invention will best be understood by reference to thedrawings, wherein like elements are designated by like alphanumericcharacter throughout.

With reference now to the accompanying drawings, FIGS. 1A-3C areprovided for general reference to assist in understanding the featuresof the embodiments of the present invention. FIGS. 1A and 1B depict arange of angles possible between the tibia and femur in a person who isextending and flexing (bending) his or her knee. Specifically, FIG. 1Adepicts a range of angles possible while the person extends and bendshis or her knee, realizing that some knees may flex to 160 degrees, 165degrees, or beyond. FIG. 1B depicts these various angles in analternative position. These figures should be kept in mind during thediscussion illustrating how with the embodiments of the presentinvention, knee flexion of greater than 135 degrees is possible for kneeprosthetic patients, which is not generally possible withcurrently-available knee prostheses.

FIGS. 2A-2C depict various perspective views of a generic kneeprosthesis 10. Specifically, FIG. 2A depicts a sagittal view of a leftknee joint having a knee joint prosthesis 10, with the tibia and thefemur of the normal knee transparent. FIG. 2B depicts an enlarged viewof a femoral component 12 of the knee prosthesis 10, while FIG. 2Cprovides a top perspective view of a tibial component 14 of the kneeprosthesis. FIG. 2B depicts certain components of the femoral component12, such a medial receiving area 16 that may be modified in embodimentsof the present invention to integrally connect with an attachment (notshown but hereinafter described) as well as a lateral receiving area 18.The internal geometry of the femoral component 12 is provided to allow aone piece femoral component 12 that is rolled into place on theresectioned femur 32, as shown in FIG. 4D. Thus, the internal geometryof the femoral component 12 includes various surfaces, including areas16 and 18, to accommodate the patellar articulation and the anteriorextensions of the proximal portions of the posterior condyles. Theresectioned portions of the condyles provide flat surfaces which areloaded in compression in full knee flexion. Additionally, theresectioned surfaces are provided such that the articular surface of thefemoral component is at essentially the same position as the surfacebeing resectioned. As such, the normal relationship between the femurand the tibia is preserved with full flexion. Additionally, when theknee is fully flexed, the interface between the femoral component andthe underlying femur is mainly loaded in compression rather than sheerforces. Compression forces provide a more stable interface between thefemoral component and the femur thereby decreasing the chances ofloosening. Therefore, in some embodiments the interface between thefemoral component and the tibial component are configured to enhance acompression force between the femoral component and the underlying femurduring full flexion of the knee joint.

Also visible in FIG. 2B is a medial femoral condylar surface 20 and alateral femoral condylar surface 22. FIG. 2C depicts the tibialcomponent 14 and its elements: a lateral tibial condylar surface 24, amedial tibial condylar surface 26, and an intercondylar surface 28. Whenthe knee prosthesis 10 is functioning, an interface exists between themedial femoral condylar surface 20 of the femoral component 12 and themedial tibial condylar surface 26 of the tibial component 14 and betweenthe lateral femoral condylar surface 22 of the femoral component 12 andthe lateral tibial condylar surface 24 of the tibial component 14.

FIGS. 3A-3C depict additional perspective views of the generic kneeprosthesis 10 with its different components. Specifically, FIG. 3Adepicts a frontal view of the knee prosthesis 10 with the femoralcomponent 12 articulating with the tibial component 14 as describedabove. FIG. 3B is a side view of the femoral component 12, and FIG. 3Cis a side view of the tibial component 14, and specifically, of themedial side of the tibial component showing the medial tibial condylarsurface 26. The medial femoral condylar surface 20 slidingly interfaceswith the medial tibial condylar surface 26 so that as a person flexes orextends his or her knee, the arc of the medial femoral condylar surface20 runs along the media tibial condylar surface 26.

In some embodiments of the present invention, greater deep knee flexionis provided to the knee prosthesis 10 by providing an articular surfaceon the proximal, anterior surface (or portion) of the posterior condylesof the femur. At least some embodiments of the present invention embracean additional or increased articular surface on the proximal, anteriorportion of either or both of the medial or lateral posterior condyles ofthe femoral component 12. Embodiments of the femoral component 12 addincreased articular surface area to the proximal end of the posteriorcondyles of the femoral component 12 in an anterior direction such thatwhen the patient bends his or her knee during deep knee flexion, contactbetween the femoral component 12 and the tibial component 14 ismaintained, and a greater, deeper knee flexion can be achieved.

Four different examples of how this may be achieved are demonstratedwith reference to the Figures. Any method of increasing an articularsurface area to the proximal end of the posterior condyles of thefemoral component 12 in an anterior direction is embraced by theembodiments of the present invention.

FIGS. 8A and 8B illustrate a femoral component 12 and method ofincreasing an articular surface area to the proximal end of theposterior condyles of the femoral component 12. FIG. 8A illustrates aside view of a conventional femoral component 12. In the firstembodiment of the inventive prosthesis, the shaded area of the femoralcomponent 12 of FIG. 8A (i.e., the posterior condyle) is thickened inthe anterior direction until the resulting surface opposing the bone isapproaching the same plane as the posterior surface of the shaft of thedistal femur. This thickening may be seen with reference to FIG. 8B. Inparticular, FIG. 8B shows that, in some embodiments, the posteriorcondyle is thickened from its posterior most edge (as illustrated byline 300) towards a plane 302 of a distal portion of posterior surfaceof the shaft of the distal femur. This results in a greater articularsurface area of the posterior condyles of the femoral component 12. Thisrequires resection of more bone but is otherwise an easy modification tocurrent prostheses and requires little to no modification of currentsurgical technique.

A second type of embodiment that extends the articular surface area isillustrated by FIGS. 4A-5C. Methods of utilizing this type of embodimentare illustrated with reference to FIGS. 9-10H. This type of embodimentutilizes an extension attachment to the femoral component 12 of anembodiment of the knee prosthesis 10, which when integrated with boththe femoral component 12 and a patient's femur, results in a greatersurface area of the femoral component 12.

As illustrated in FIGS. 4A-5D, this type of embodiment has a modularattachment 30 that provides a modular flexion attachment surface toextend the articular surface area of the anterior portion of theproximal portion of the posterior condyles. The modular attachment 30may be attached to the inside, or non-articular surface, of a relativelyconventional total knee femoral component 12. The modular attachment 30has a portion that may be partially received, in one embodiment, withina recessed receiving area on the flat anterior surface of one or both ofthe posterior condyles of the femoral component 12 and may thus be usedon the medial posterior condyle, the lateral posterior condyle, or both.Alternatively, it may be implanted in a groove within either or both ofthe resected posterior condyles of the femur itself.

The modular attachment 30 provides an increased articular contact areaas an anterior continuation of the medial femoral condylar surface 20and/or of the lateral femoral condylar surface 22 of the femoralcomponent 12. In some embodiments, the modular attachment 30 may beinitially placed onto the femoral component 12 and then attached to thedistal end of the patient's femur. In other embodiments, the modularattachment 30 may be connected first to the posterior condyles of thedistal end of the femur and then integrally connected with the femoralcomponent 12. The modular attachment 30 may be used on the medial side,on the lateral side or on both sides.

FIGS. 4A-4D depict perspective views of embodiments of the femoralcomponent 12 and the modular attachment 30. As described, the modularattachment 30 attaches to the femoral component 12 and to the femur of apatient to enlarge the surface area of the femoral component 12 and,ultimately, to enable deep knee flexion beyond 140 degrees in a kneeprosthesis patient. FIG. 4A depicts a simplified side view of anembodiment of the femoral component 12 having the modular attachment 30attached to the posterior condyle of the femoral component. FIG. 4Ddepicts a side view of the attachment integrally attached to a patient'sfemur and to the femoral component of the knee prosthesis. The modularattachment 30 may be modular as shown in FIGS. 4B-4D and may fit withina recess in either or both of the medial receiving area 16 and thelateral receiving area 18 (i.e., in the anterior interior surface of theposterior condyles of the femoral component 12, as shown in FIG. 2B)and/or in either or both of the medial and the lateral posteriorcondyles of the femur or in both the femoral component 12 and the femur.In another embodiment the modular attachment 30 may be a permanent partof the femoral component, as discussed below.

FIG. 4B depicts a side view of one embodiment the modular attachment 30and FIG. 4C depicts a top view of the depicted embodiment of the modularattachment 30. Specific dimensions of the depicted embodiment of themodular attachment 30 are not given and one of skill in the art willrecognize that the dimensions may be modified from patient to patientand will also recognize that the various portions of the modularattachment 30 may all be formed in some embodiments to be as wide as thecondyle of the femoral component 12.

In some embodiments, the modular attachment 30 includes a first portionroughly perpendicular to a second portion. The first portion of themodular attachment 30 entails a flanged articular area 36 (“flanged area36”) at one end of the modular attachment 30, and an elongated stem 38extending therefrom, which extends roughly perpendicular from theflanged area, distally from the flanged area 36. The elongated stem 38therefore is attached to the non-articular side of the flanged area 36.Although the elongated stem is illustrated in FIG. 4C as having amedial-lateral width substantially shorter than the medial-lateral widthof the flanged area 36, the elongated stem 38 of other embodiments maybe of any medial-lateral width up to the medial-lateral width of theposterior condyles of the femoral component 12 itself.

The elongated stem 38 has an upper side 40 and a lower side 42. Nodules44 may be placed on either or both of the upper side 40 and the lowerside 42, to enable an integral connection with the femur 32 on the upperside 40, and the femoral component 12 on the lower side 42. Some form ofa nodule-receiving groove or recess (not shown) may be made in the femur32 and/or the femoral component 12 to receive these nodules 44 and tosecure the integral connection between the femur 32, the attachment 30,and the femoral component 12; with the modular attachment 30 beingdisposed between the femur 32 and the femoral component 12.

In embodiments having no nodules 44 on the elongated stem 38, theattachment 30 may fit within a recess made on either or both of themedial receiving area 16 and the lateral receiving area 18 of thefemoral component 12. The elongated stem 38 of the modular attachment 30would fit within such recesses and integrally connect thereto. Themodular attachment 30 may simultaneously connect with the femur 32 onthe upper side 40 (generally) of the elongated stem 38. In embodimentshaving no nodules on the elongated stem, the stem of the modular portionmay further fit into a groove prepared in the resected posteriorcondyles of the femur.

The modular attachment 30 increases the overall surface area of thefemoral component 12 and prolongs the interface and contact that existsbetween the femoral component 12 and the tibial component 14. Thisenables greater knee flexion in prosthetic knee patients because thefemoral component 12 remains interfaced with the tibial component 14throughout the full range of flexion resulting in pain-free kneeflexion.

Without this increased surface area, the medial and lateral proximaledges of the posterior femoral condyles of a prosthesis may push intothe proximal surfaces of the tibial component 14 and may produce wear ofthe tibial component 14. In addition, the tibial component 14 maycontact the bone of the distal femur 32 that is anterior and/or proximalto the proximal edges of the posterior condyles of the prosthesis andcause pain to and limit flexion of the prosthetic knee patient and maycause wear to the tibial component. Further, without this added surfacearea, with flexion beyond 140 degrees, the tibial component 14 may exerta force in the distal direction on the femoral component 12, which mayresult in loosening of the femoral component 12. Therefore, the modularattachment 30 extends the life of the prosthetic knee, decreases pain tothe patient, and ultimately, enables a prosthetic knee patient toachieve deep knee or full functional flexion.

FIGS. 5A-5D depict various perspective views of the modular attachment30 as it is attached to the femoral component 12 and to the femur 32.FIG. 5A is illustrative of the modular attachment 30 as it is attachedto the femur 32 prior to attachment of the femoral component 12. FIGS.5B-5D are illustrative of the modular attachment 30 as it is recessedwithin the femoral component 12 prior to attachment to the femur 32, andspecifically, as the modular attachment 30 is integrally connected toeither or both of the medial femoral receiving area 16 and the lateralfemoral receiving areas 18.

FIG. 9 and FIGS. 10A-10H illustrate methods of attaching the modularattachment 30 to the femur 32, followed by attaching the femoralcomponent 12 to the femur 32 and modular attachment 30. FIG. 9illustrates the resection needed on the femur 32 prior to creating therecess in the femur to allow attaching the modular attachment 30. FIG. 9and FIGS. 10A-10H do not illustrate the specific resection needed forthe modular attachment 30, but the resection needed will be appreciatedby one of skill in the art. After resection is completed, as at FIG.10A, the modular attachment 30 may be attached to the femur as at FIG.10B. The femoral component 12 may then be attached to the femur 32 (andto the modular attachment 30, if desired) by positioning and moving thefemoral component 12 as illustrated in FIGS. 10C-10H. As may beappreciated from the sequence of illustrations depicted in FIGS.10C-10H, the femoral component 12 needs to be rotated or rolled intoposition, with initial contact beginning in the posterior region asillustrated in FIG. 10E and progressing to the fully-seated positionillustrated in FIG. 10G. This is a new implantation technique that willrequire some additional practice and training over current techniques.

As has been set forth above in reference to FIG. 4A, a third type ofembodiment having an extended articular surface is not modular and doesnot utilize a separate modular attachment 30. In such embodiments, anextended articular surface corresponding to the flanged area 36 of themodular attachment 30 may be integrally formed as part of one or bothcondyles of the femoral component 12. Placement of one such embodimentis illustrated with reference to FIGS. 11A-11K. As may be appreciatedwith reference to these Figures, placement of such an embodiment alsoutilizes a similar rotational placement technique to that illustrated inFIGS. 10C-10H. As may be appreciated by reference to FIGS. 10H and 11K,any of the modular or non-modular embodiments may, optionally, befurther secured by one or more screws placed in an anterior flange ofthe femoral component 12.

One advantage of the embodiment illustrated in FIGS. 11A-11K is that theimplanting surgeon may decide whether to utilize the illustratedembodiment or a traditional femoral component 12 after the distal andanterior oblique cuts have been made. This is illustrated in FIGS. 12Athrough 12C. FIG. 12A shows a traditional femoral component 12. FIG. 12Bshows an embodiment of the described femoral component 12 without anextended anterior flange. In other words, FIG. 12B shows that, in someembodiments, when the femoral component is seated on the femur 32, aproximal anterior end 69 of the femoral component is configured toterminate at or near a proximal end 71 of the anterior oblique cut 64(e.g., at between about 0 and about 15 mm on either the proximal side orthe distal side of the proximal limit of the knee's natural articularcartilage). FIG. 12C, on the other hand, shows an embodiment of thefemoral component 12 illustrated in FIGS. 11A-11K, which include ananterior flange 49 that extends proximally past the anterior oblique cut64. As may be appreciated by reference to the Figures, the distal cuts62 and anterior oblique cuts 64 are essentially identical. This may befurther appreciated by reference to FIG. 13, which shows a superimposedview of FIGS. 12A and 12B, not only showing that the distal femoral cuts62 and the anterior oblique cuts 64 are identical, but also showing thatthe total amount of bone resected for the illustrated embodiment issimilar to or less than the amount resected using current techniques andfemoral components 12.

In a non-modular embodiment of the femoral component 12 as shown inFIGS. 11A-11K and in a modular embodiment of the femoral component asshown in FIGS. 4A-5D, there are junctions where the inside flat surfacesof the prosthesis (which when implanted are in contact with the bone)meet. These flat surfaces, rather than coming together at a sharp angle,may or may not have a radius connecting the two flat surfaces. Not allof the junctions of the flat surfaces necessarily need a radius and insome embodiments none of the junctions of flat surfaces will have radii.The flat surfaces may or may not be in exactly the same planes as onconventional knees and will provide for the placement of a non-modularsurface that will provide an articulation for the proximal, anteriorportion of the posterior femoral condyles extending to or almost to aplane that is a continuation of the posterior cortex of the distalfemoral shaft. In embodiments where one or more radii are provided tothe junction(s) of the inside flat surfaces of the femoral component 12,corresponding radii 31 or curvatures may be provided to the resectedbone surface of the femur, as is illustrated in FIG. 5A. As may beappreciated by one of skill in the art, the presence of thecorresponding radii 31 may assist in the rotational placement of thefemoral component 12 as illustrated in FIGS. 10A-10H and 11A-11K.

This internal configuration allows the femoral component 12 to beinitially applied to the femur in a flexed position and then rotatedinto the fully extended position as it is implanted fully, asillustrated and discussed with reference to FIGS. 10A-10H and 11A-11K.Screw(s) may, optionally, be placed in the anterior flange (or otherportion) of the femoral component 12 to firmly stabilize the component.This ability facilitates implanting the non-modular femoral component 12or a modular femoral component 12 with the modular attachment 30 alreadyimplanted on the posterior condyles of the femur 32.

A fourth type of embodiment of the femoral component 12 is illustratedin FIG. 14. This type of embodiment has a femoral component 12 thatreplaces the weight-bearing distal femoral condyles, and some or all ofthe anterior femoral articular surface and, in addition to some or allof the articular surface of the posterior condyles extending proximallyand anteriorly to an area that is in the same plane as a continuation ofthe posterior cortex of the distal one fourth to one third of the femur.Such an embodiment may comprise separate medial and lateral componentsor they may be attached together to form one component that replaces orresurfaces the medial and lateral condyles.

Historically, many early total knee femoral components 12 did nothingregarding the patello-femoral joint. Because a certain percentage ofthose patients had anterior knee pain, an anterior flange was added tothe femoral component 12 to resurface the trochlea (patellar groove).This weakened the patella and resulted in fractures in some patients.Recently techniques have been developed to minimize patellar pain whichdo not require implantation of a component. The embodiment shown in FIG.14 does not have an anterior flange that is an integral part on thecondylar portion of the prosthesis. It is anticipated that such a device12 alone may, in some patients, be adequate to replace the femoralcondyles and allow the surgeon to treat the patello-femoral joint ashe/she felt was indicated. Alternatively, a separate patello-femoralarticular surface or surfaces could be implanted. The patello-femoralimplant(s) could be entirely separate or could be modular and attachedto the device shown in FIG. 14. In some instances, the embodimentillustrated in FIG. 14 includes the ability to attach a modular anteriorflange (trochlear groove) to the device shown in the Figure. In thisregard, FIGS. 16T-16W (discussed below) illustrate some methods forattaching various embodiments of a modular anterior flange 57 (ormodular patella-femoral component).

Implementations of the present invention embrace a femoral component 12,a tibial component 14, a modular attachment 30, stem 500 (discussedhereafter), and/or any other suitable components that each comprise ametal, metal alloy, ceramic, carbon fiber, glass, polymer (including,without limitation, bone cement, nylon, polyethylene, polyester,polytetrafluoroethylene (Teflon®), and/or any other suitable polymer),organic material, retrieved human or animal tissue, cementless material,and naturally occurring or synthetic materials used either separately orin any combination of two or more of the materials.

As may be appreciated by reference to the above discussion and thecorresponding Figures, currently-existing femoral components 12 providean articular surface that only extends a short distance in the proximalanterior direction of the posterior condyle. For example, as may be seenwith reference to FIGS. 2A and 8A, the articular surface at the anteriorend of the posterior condyle typically extends to and replaces at mostthe posterior third of the posterior condyle, as measured from the mostposterior portion of the patient's original posterior condyle (or fromthe most posterior portion of the femoral component 12) to a plane thatis a continuation of the distal one fourth to one third of the posteriorcortex of the femoral shaft.

In contrast, the various embodiments of the femoral component 12illustrated in the Figures and discussed above provide an extendedarticular surface for either or both of the medial condyle and thelateral condyle that extends in a proximal anterior direction so as toextend half or more of the anteroposterior distance between the mostposterior portion of the posterior condyle and the plane that is acontinuation of the distal one fourth to one third of the posteriorcortex of the femoral shaft. In some embodiments, the extended articularsurface extends at least two-thirds of the anteroposterior distancebetween the most posterior portion (e.g., as shown by line 300 in FIG.8B) of the posterior condyle and the plane (e.g., as shown by line 302in FIG. 8B) that is a continuation of the distal one fourth to one thirdof the posterior cortex of the femoral shaft. In other embodiments, theextended articular surface extends nearly the entire anteroposteriordistance between the most posterior portion of the posterior condyle andthe plane that is a continuation of the distal one fourth to one thirdof the posterior cortex of the femoral shaft. In still otherembodiments, the extended articular surface may extend even further, toencompass a distal portion of the posterior cortex of the femoral shaft,as illustrated in FIGS. 16A-16D.

The surface of the extension, which may or may not contact bone and is acontinuation of the femoral articular surface, can be referred to as thefull flex articulation. There may be a corresponding surface on theposterior edge of the medial and or lateral tibial articulation which isnot part of the articular surface of the tibia when the tibia is in fullextension. For example, in some implementations of the current inventionthere is a corresponding surface on the posterior edge of the medialtibial articulation where the center of the medial articular surface ismore than 20% of the distance from the posterior edge of the componentto the anterior edge.

The embodiment illustrated in FIG. 19A shows a non-articular surface 41posterior to the main articular surface 43. FIG. 19B illustrates a fullflex articular surface 45 and an articular surface 47. The tibial fullflex articulation of FIG. 19B is posterior to the main weight bearingarticulation and articulates with a specific articular area on thefemoral component, the femoral full flex articulation (proximalextension 50) shown in FIGS. 16A-16Q and shown in a slightly shortenedembodiment in FIG. 16E.

With continued reference to FIG. 16E, in some embodiments of the presentinvention the articular surface 402 of femoral component 53 comprisessections of various surface radii 404, 406 and 408. Each section isprovided as a means for controlling the relationship between the femoralcomponent 53 and the tibial component (not shown) throughout the rangeof flexion for the knee. However, in some embodiments, radius 406 may beconstant and replace radii 404 and 408.

Radius 404 is characterized as having a decreasing radius such that anindentation 410 is formed on the articular surface 402. In someembodiments, indentation 410 is configured to receive anterior ridge 420of tibial component 14 when the knee joint is hyper extended toapproximately −10°, as shown in FIG. 16F. Upon further hyperextension,as shown in FIG. 16G, indentation 410 further impinges upon anteriorridge 420, such that the interface between indentation 410 and anteriorridge 420 acts as a fulcrum between femoral component 53 and tibialcomponent 14. Therefore, as the knee joint is hyper-extended beyondapproximately −10°, radius 404 of the articular surface 402 isdistracted from the tibial component 14, as shown. As this distractionincreases, the dense connective tissues of the knee joint are stressedthereby limiting further hyper-extension of the knee joint.

Referring now to FIG. 16H, a knee joint is shown in a neutral, extendedposition at approximately 0° flexion. At approximately 0° flexion, radii404 and 406 are partially in contact with tibial articular surface 403,yet the knee joint is not fully constrained. As such, femoral component53 is permitted to move anteriorly and posteriorly relative to thetibial component 14. In some embodiments, radii 404 and 406 providelaxity within the knee joint between approximately 0° and 20° flexion.In other embodiments, radii 404 and 406 provide laxity within the kneejoint between approximately 0° and 40° flexion.

Referring now to FIG. 16I, a knee joint is shown at approximately 10°flexion with the femoral component 53 being shifted anteriorly relativeto tibial component 14. FIG. 16J shows a knee joint at approximately 10°flexion wherein the femoral component 53 has been shifted posteriorlyrelative to tibial component 14. Anterior and posterior laxity withinthe knee joint, as provided by radius 404, is limited both by tensionwithin the dense connective tissues of the knee joint, and by thecurvatures of the opposing femoral and tibial articular surfaces 402 and403. By providing laxity between approximately 0° and approximately 20°the natural mechanics of knee flexion are preserved, as sensed orexperienced by the user. In some embodiments, laxity is eliminatedbetween approximately 0° and approximately 20°, thereby modifying thenatural mechanics of knee flexion as may be desired. This is achieved byhaving radii 404 and 408 replaced by radius 406.

Upon further flexion of the knee joint to approximately 20°, radius 406is largely in contact with tibial articular surface 403, as shown inFIG. 16K. However, in some embodiments laxity within the knee joint ismaintained at approximately 20° flexion such that the femoral component53 is permitted to shift anteriorly (FIG. 16K) and posteriorly (FIG.16L) relative to the tibial component 14. As the knee joint is furtherflexed, radius 406 assumes full contact with the opposing tibialarticular surface 403 thereby fully constraining anterior and posteriormovement within the knee joint, as shown in FIG. 16M. Full contact andconstraint within the knee joint is thereafter maintained through theremaining mid-flexion movement of the joint, as shown in FIGS. 16N and16O. Beyond approximately 110° flexion, radius 408 begins to pick upcontact with tibial articular surface 403 thereby causing distraction ofthe femoral and tibial components 53 and 14, as shown in FIG. 16P. Asthe knee joint is further distracted, proximal extension 50 maintainscontact with posterior articular feature 412 of the tibial component 14.

With reference to FIG. 16Q, a representative embodiment of aunicompartmental femoral component 120 is shown. The various componentsof the present invention may be substituted with a unicompartmentalcomponent, as discussed below. In some embodiments, unicompartmentalfemoral component 120 further comprises a decreasing radius 404providing indentation 410, as shown in FIG. 16R. In other embodiments,unicompartmental femoral component 120 is truncated thereby providingindentation 410 at intersection between component 120 andnon-resectioned anterior condylar surface of femur 32, as shown in FIG.16S.

The unicompartmental component is generally implanted to replace theweight bearing portion of the knee joint medially or laterally. Theunicompartmental component may be used medially and/or laterally as twoseparate femoral and two separate tibial components on just the weightbearing portion of the joint. In some embodiments, the unicompartmentalcomponent is used with two femoral or two tibial components joined, butignoring the patello-femoral joint. In other embodiments, theunicompartmental component is used as one femoral component replacingthe medial and lateral weight bearing portions of the distal femur andalso a portion of, or all of the patello-femoral joint with either a onepiece tibial component or separate medial and lateral tibial components.Finally, in some embodiments the unicompartmental component is aone-piece, femoral component replacing the patello-femoral joint andeither the medial or lateral weight-bearing portion of the femur.

In some embodiments, the unicompartmental component 120 includes a fullflex femoral articulation surface 50. As previously discussed, thearticulation surface or extension 50 is configured to provide extendedcontact between the unicompartmental femoral component 120 and a fullflex tibial articulation surface 55 of a tibial component during deepflexion of the knee. In some embodiments, a portion of the poplitealsurface 202 of the femur is removed to accept placement of thearticulation surface 50. In other embodiments, a unicompartmentalcomponent (not shown) is provided for use in conjunction with a modularfull flex femoral articulation surface (not shown). Thus, in someembodiments a first portion of the femur is prepared to receive theunicompartmental component 120, and a second portion of the femur isprepared to receive a modular full flex femoral articulation surface(not shown). As such, a combination of the unicompartmental componentand the modular full flex femoral articulation surface provide aunicompartmental femoral component that is functionally equivalent tothe unicompartmental femoral component 120.

In some embodiments, the unicompartmental femoral component 120 is usedin conjunction with a unicompartmental tibial component. In otherembodiments, the unicompartmental femoral component 120 is used inconjunction with a full tibial component. Finally, in some embodiments,the unicompartmental femoral component 120 is used directly inconjunction with a natural surface of the opposing tibia.

Where permitted, implementation of a unicompartmental femoral component120 provides several advantages over total knee replacement procedures.For example, while an eight-inch incision is typically required for atotal knee replacement surgery, a partial knee replacement utilizing aunicompartmental femoral component 120 requires an incision ofapproximately three-inches. Thus, one benefit of a unicompartmentalfemoral component 120 is decreased scarring following the partial kneereplacement procedure.

Other benefits of a partial knee replacement include decreased recoverytime, increased range of motion, and decreased overall damage to theknee. A total knee replacement procedure may require the patient toremain in the hospital for up to four days. It can also take up to threemonths, or longer, to recover from the surgery. However, with a partialknee replacement procedure, a patient typically requires no more thantwo days of hospitalization followed by one month of recovery.Additionally, a patient is typically able to walk without assistance aweek or two following the partial knee replacement procedure.

Unlike some total knee replacement procedures, insertion of theunicompartmental femoral component 120 generally preserves moreligaments thereby providing a fuller range of motion. For example, insome partial knee replacement procedures, the anterior and/or posteriorcruciate ligaments are preserved, as desired. A partial knee replacementalso generally results in less damage to the knee because the surgery isminimally invasive thereby causing minimal tissue, muscle and tendondamage to the knee.

For some partial knee replacement procedures, various methods may beimplemented to address pain and discomfort caused by patello-femoralarthritis. For example, for some partial knee replacement proceduresdenervation of the patella is performed. In other partial kneereplacement procedures, denervation of the opposing femoral groove isperformed. In some embodiments of the present invention theunicompartmental femoral component 120 is designed to reproduce thenatural patello-femoral joint throughout the range of motion and tofacilitate tracking of the patella in the femoral groove. In otherembodiments, a combination of denervation and natural design of theunicompartmental femoral component 120 are implemented to adequatelyaddress the patello-femoral arthritis.

The interaction of the femoral full flex articulation 50 and the tibialfull flex articulation 55 is illustrated in FIGS. 20A-20I, wherein FIGS.20A-20E are at 0 degrees, FIG. 20F is at 90 degrees, FIG. 20G is at 130degrees, FIG. 20H is at 150 degrees, and FIG. 20I is at 160+ degrees.FIG. 20B identifies a representative position of unresected tibialplateau 51. FIG. 20C identifies a representative closing radius on aposterior portion of a femoral component 53. FIG. 20D identifies arepresentative full flex femoral articulation 50. FIG. 20E identifies arepresentative full flex tibial articulation 55. FIG. 20H identifies arepresentative approach of the full flex femoral articulation 50 to thefull flex tibial articulation 55 during flexion. FIG. 20I identifies arepresentative contact of the full flex femoral articulation 50 to thefull flex tibial articulation 55 during deep flexion.

FIGS. 15A-15D illustrate the various manners in which the fourpreviously-discussed embodiments of the femoral component 12 provide anextended articular surface 48. The concept of adding more articularsurface to the proximal portion of the posterior condyles of the femoralcomponent may be generally accomplished by extending the proximalportion anteriorly until the articular surface approaches, or extendsbeyond the plane of the posterior surface of the shaft of the distalfemur, if that plane were to extend distally. For example, as may beseen from FIGS. 15A-15D, the extended articular surface 48 of eachembodiment extends the articular surface at the anterior end of one orboth of the medial posterior condyle or the lateral posterior condyle.As illustrated in FIGS. 16A-16D, the articular surface may be furtherextended in a proximal direction from the end of the extended articularsurface 48. This further extension may be provided by a proximalextension 50. The proximal extension 50 may be an integral part of thefemoral component 12, it may be a part of the modular attachment 30 (asdiscussed herein), or it may be provided as a separate and additionalcomponent. In one embodiment where the proximal extension 50 isprovided, the proximal extension 50 acts as a fulcrum that interactswith the tibia or with the tibial component 14 to increase separationbetween the femur 32 and the tibia during full functional flexion toimprove the deep knee flexion. In another embodiment, the proximalextension 50 allows the normal relationships between the tibia and femurin full functional flexion to exist while maintaining contact betweenthe two surfaces.

Where the femoral component 12 comprises a proximal extension 50 (or afemoral full flex articulation), the proximal extension can comprise anysuitable shape. Indeed, in some embodiments (as illustrated by at leastFIG. 16F, the proximal extension 50 extends from the femoral component12 such that a concave articulation surface 17 (or a concave surface ofany shape that is suitable for articulating against a portion of thetibia and/or tibial component 14) is disposed at or near a proximal,posterior portion of the femoral component 12. In some embodiments, FIG.16G illustrates that the proximal extension 50 comprises a first curvedarticular surface 19, while the femoral component's posterior condylarsurface (e.g., a lateral and/or medial condylar surface) comprises asecond curved articular surface 21, wherein the first 19 and the second21 articular surfaces form a reverse curve.

Additionally, where the femoral component 12 comprises a proximalextension 50, the proximal extension can be disposed in any suitablelocation on the femoral component that allows the concave articulationsurface 17 to articulate against a portion of the tibia and/or thetibial component 14 when the knee is in (or is approaching) fullflexion. Moreover, the proximal extension 50 can also be used inconnection with any suitable femoral component (e.g., as a modular unitor as an integral part) that allows the proximal extension to functionas described herein.

In some embodiments, the proximal extension 50 extends from the femoralcomponent 12 so that the concave articulation surface 17 is disposed ator near a proximal, posterior portion of the femoral component (e.g., asshown in FIGS. 16A-16D). Indeed, in one illustration, FIG. 16D showsthat in an embodiment in which the femoral component 12 has a firstinternal surface 721 for contacting an anterior femoral surface and/orcut 621 on the femur 32, a second internal surface 722 for contacting ananterior chamfer cut 622 on the femur, a third internal surface 723 forcontacting a distal cut 623 on the femur, a fourth internal surface 727for contacting a posterior chamfer cut 627 on the femur, a fifthinternal surface 724 for contacting a full flexion cut 624 on the femur(or a cut that runs proximally and anteriorly from its distal endtowards a posterior surface of the femur), the proximal extension 50 isdisposed near the fifth surface 724 (e.g., so as to be disposed at ornear a proximal, posterior portion of one or both of the condylarsurfaces of the femoral component 24 and/or at or near a poplitealsurface of the shaft of the femur).

In other embodiments, FIGS. 16X-16Z show that, in some cases, theproximal extension 50 is disposed on a femoral component 12 that lacks asurface (e.g., surface 624) for contacting a full flexion cut 624 on thefemur 32. In such embodiments, the proximal extension 50 can be disposedin any suitable location that allows it to perform its intendedfunctions. Indeed, in some embodiments in which the femoral component 12comprises a first internal surface 721 for contacting the anteriorsurface 621 of the femur 32, a second internal surface 722 forcontacting an anterior chamfer cut 622 on the femur, a third internalsurface 723 for contacting a distal cut 623 on the femur, a fourthinternal surface 727 for contacting a posterior chamfer cut 627 on thefemur, and an additional internal surface 728 for contacting a posteriorcondylar cut 628 on the femur (e.g., a cut that runs substantiallyparallel to, or that diverges by any suitable amount of less than about50 degrees (e.g., any suitable amount less than 40 degrees) from thefirst interior surface 621), the proximal extension 50 is disposedproximal to surface 628.

Thus, FIGS. 16X-16Z show that conventional femoral components can easilybe modified to include a femoral full flex articulation (e.g., by theaddition of a modular and/or integral proximal extension 50). It shouldbe noted that while FIGS. 16X-16Z show the femoral component 12 having aproximal extension 50 that is being used to articulate and/or act as afulcrum against the tibial component 14 (e.g., a component comprising atibial full flex articulation), such a femoral component can be used toarticulate against an any suitable tibial articulation surface (e.g.,from a unresected tibia, a partially resected tibia, and/or any suitabletibial component that can articulate with the proximal extension 50).Additionally, while FIGS. 16X-16Z show some embodiments in which theproximal extension is formed as an integral portion of the femoralcomponents, in some embodiments (as described herein), the proximalextension comprises a modular unit that is attachable to the femoralcomponent.

Thus, in some embodiments of the present invention, greater deep kneeflexion is facilitated by providing an articular surface on the proximalposterior and/or anterior surfaces (or portions) of one or both of theposterior condyles of the femur. At least some such embodiments embracean additional or increased articular surface on the proximal posteriorand/or anterior portion (e.g., as shown in FIGS. 16A-16S and 16X-16Z) ofeither or both of the medial or lateral posterior condyles of thefemoral component 12. Indeed, some embodiments of the femoral component12 add increased articular surface area to the proximal end of theposterior condyles of the femoral component 12 (e.g., in an anteriordirection such that when the patient bends his or her knee during deepknee or full functional flexion, contact between the femoral component12 and the tibial component 14 is maintained, and a greater, deeper kneeflexion may be achieved.

In at least some embodiments of the present invention, greater deep kneeflexion may be provided or improved by modifying the tibialarticulation, in which the center of the conforming medial tibialarticular surface of the tibial component 14 is moved posterior relativeto what is currently available. Additionally, in some such embodiments,the overall shape of the lateral and/or medial tibial articular surfacesmay be modified. This is illustrated with reference to FIGS. 6A-6D and6J-6K.

In some such embodiments of the tibial component 14, the condylar orarticular plateau surfaces are asymmetric. Indeed, in some embodiments,the lateral undersurface side of the tibial component 14 is shorter inthe anteroposterior dimension than the medial side, and the top of thetibial component 14 may also be asymmetric.

Anatomically, the tibial plateau typically has a greater anteroposteriordimension medially than it has laterally. In order to cover as much ofthe cut proximal tibia as possible and avoid anterior or posterioroverhang of the lateral plateau, in some instances, the tibial componentis larger in the anteroposterior dimension medially than it islaterally. In one embodiment, this is accomplished by moving the centerof the medial articular surface posteriorly to compensate for thedimensional differences. In some cases, in order to achieve fullflexion, it can be useful to have the medial center of rotation on thetibia (which is a concave segment of a sphere) more posterior than iscurrently available with other designs. This allows the proximal tibia,when the knee is flexed beyond approximately 120-130 degrees, to bepositioned anteriorly enough so that there is no impingement of theposterior edge or portion of the medial tibial articular surface on theproximal portion of the posterior medial condyle of the femur. Currentdesigns of tibial components 14, which will allow the tibia to moveanterior with flexion, either have a non-spherical medial tibialarticular surface or the center of rotation of the spherical articularsurface is not as far posterior as is provided by the embodimentsdescribed below. However, embodiments of the current invention may beused in combination with any knee replacement design that will allowknee flexion to 120° or greater.

Currently, some available total knee tibial components 14 that have afixed center of rotation medially, have the center of rotation locatedat a position that is around 35-45% of the entire anteroposteriordimension from the posterior surface of the tibial component 14.Nevertheless, in some embodiments of the tibial component 14 describedherein, the center of rotation is moved posteriorly so that it isbetween about 18% and about 35% of the anteroposterior dimension fromthe posterior wall of the tibial component 14. In such embodiments, thecenter of rotation can be disposed in any location between about 18% andabout 35% (or any sub-range thereof) of the anteroposterior dimension ofthe tibial component 14, as measured from the component's posterioredge. Indeed, in one non-limiting example, the center of rotation of thefemur with respect to the tibial component is between about 20% andabout 33% of the anteroposterior dimension from the posterior edge ofthe tibial component 14.

In the normal knee, the medial side of the knee is constrained in thatfor any degree of flexion the position of the medial femoral condylerelative to the tibial articular surface is roughly fixed and does notmove anteriorly or posteriorly a significant amount in the flexion rangeof roughly 20-130 degrees. In contrast, on the lateral side, except forfull extension and sometimes full flexion, after around 20-40 degrees offlexion the lateral femoral condyle can move anterior and posterior onthe lateral tibial plateau. In full functional flexion to 160 degreesand beyond, the lateral femoral condyle may appear to be touching onlythe most posterior portion of the opposing tibial plateau or it maycontact the plateau more anterior clearly on the flattened portion ofthe lateral tibial plateau.

Therefore, in embodiments of the tibial component 14, the lateral tibialarticular surface is basically flat in the anteroposterior sense, exceptanteriorly where there is an anterior lip which prevents the tibialcomponent from rotating too far externally and allowing the lateralfemoral condyle to slide off the anterior edge of the tibial component.In some embodiments, the basically flat portion of the lateral tibialarticular surface may comprise between about two-thirds and aboutseven-eighths (or any sub-range thereof) of the total anteroposteriordimension of the tibial component 14. In some embodiments, a slight lipmay be present posteriorly on the lateral side, however, as long as thefixed center of rotation is positioned as described, no lip is requiredposteriorly on the lateral side. In other embodiments there is noanterior or posterior lip. In some embodiments, the lateral tibialarticular surface is either flat or concave when viewed in the frontalplane and, if concave, may or may not be the same radius of curvature ofthe opposing femoral condyle or it may have a greater radius when viewedin the frontal plane. In some cases, this flat or concave groove is flaton the bottom when viewed in the sagittal plane, except for the anteriorand posterior ends as noted above and is generated around a point thatcorresponds to the center of rotation of the medial condyle. In someembodiments, the posterolateral tibial articulation may be the same asdescribed for the medial posterior full flex articulation. In otherembodiments, the medial tibial articular surface may be the same as, orsimilar to the flat articular surface described for the lateral tibialplateau. However, in some embodiments, the position of the medialarticular contact is mainly obligatory while the position of the lateralarticular contact is non-obligatory. Thus, the position of the lateralarticular contact is likely determined by the task being performed, bycomfort, and/or by culture.

FIGS. 6A-6D and 6J-6K depict a comparison of a prior art tibialcomponent 14's medial tibial condylar surface 26 and lateral tibialcondylar surface 24 with some embodiments of the tibial component 14 asdiscussed above. Specifically, FIGS. 6A and 6B reflect side views ofmedial and lateral sides (respectively) of some currently availabletibial components 14, while FIGS. 6C and 6J illustrate side views ofmedial sides, and FIGS. 6D and 6K illustrate side views of lateral sidesof some embodiments of the tibial component 14, as discussed above. Itwill be appreciated that a number of varied configurations for themedial and lateral articular surfaces ranging from almost flat, bothmedially and laterally, to more conforming, as shown in FIGS. 6A and 6B,have been used in the past; however, it is currently believed that nonehave either a combination of a posteriorly-displaced medial articularsurface and a relatively-flat lateral articular surface, or a medialfemoral full flex tibial articulation. These configurations permit thelateral femoral condyle to move anteriorly and posteriorly on thelateral tibial articular surface as the knee flexes and extends. Otherconfigurations may be provided, so that as long as the lateral tibialarticular surface will allow this anteroposterior motion, the lateraltibial configuration does not need to be confined to a singleconfiguration, as shown in FIGS. 6D and 6J.

The lateral tibial articulation may in some embodiments have noposterior lip, and in other embodiments the posterior surface may slopedownward when it is accompanied by a medial tibial articulation thatprovides for flexion beyond 135 degrees.

In the prior art tibial component 14, the condylar surface has acurvature centered on a fixed point 52. The distance from the fixedpoint 52 (or from the low point of the curvature centered on the fixedpoint 52) to the posterior edge 54 of the tibial component isapproximately 35-45% of the anteroposterior dimension of the tibialcomponent 14. These measurements are similar for the medial (FIG. 6A)and lateral (FIG. 6B) sides of the tibial component 14. Some currentlyavailable tibial components 14 have a lip 56.

In the embodiment of the tibial component 14 illustrated in FIGS. 6C and6D, there is no tibial component lip 56 associated with the medialcondylar surface 26. Rather, the medial tibial condylar surface 26 runsalong a smooth arc. As the arc is generated, a low lip may be present insome embodiments and may extend up to and include the tibial full flexposterior articulation. The amount of the lip will be determined by therelationship of the center of rotation to the posterior edge 54 of thetibial component 14. In another embodiment, however, FIG. 6J shows animplementation in which the tibial component 14 (e.g., at the medialtibial condylar surface 26) comprises a lip 56 at the end of a smootharc.

Though the radius from fixed point 52 to the articular surface in FIGS.6A and 6C is essentially the same, in some embodiments of the currentinvention, the distance from the fixed point 52 (or from the low pointof the curvature centered on the fixed point 52) to the posterior edge54 of the tibial component 14 is shorter. Indeed, as mentioned earlier,in some embodiments, the fixed point 52 is disposed at any locationbetween (or sub-range of) approximately 18% and less than approximately35% of the anteroposterior dimension from the posterior end of thetibial component 14, as may be seen in FIGS. 6C and 6J. For instance, insome non-limiting embodiments of the current invention, the distancefrom the fixed point 52 to the posterior edge 54 of the tibial component14 is between about 20% and about 30% (e.g., about 28%±1.5%).

With respect to the lateral side of the tibial component 14, in theembodiment illustrated in FIGS. 6D and 6K, there is both an anterior lip58 and a small posterior lip 60. In alternate embodiments, the posteriorlip 60 may be omitted as discussed above. Additionally, with respect toFIG. 6J, in some embodiments, the posterior lip 56 can raise anysuitable amount above the lowest point (e.g., fixed point 52) in thetibial articulation surface (e.g., medial tibial condylar surface 26).Indeed, in some embodiments, the posterior lip rises between about 0.5and about 8 mm (or any sub-range thereof) above the lowest point in themedial tibial condylar surface 26. Indeed, in some embodiments, theposterior lip rises between about 2 and about 6 mm (or any sub-rangethereof) above the lowest point in the medial tibial condylar surface26. Moreover, in some embodiments, the posterior lip rises between about3 and about 5 mm (or any sub-range thereof) above the lowest point inthe medial tibial condylar surface 26.

Thus, as has been illustrated with reference to FIGS. 6A-6D and 6J-6K,in at least some embodiments of the present invention, greater deep kneeflexion may be provided or improved by modifying the tibialarticulation, in which the center of the conforming medial tibialarticular surface of the tibial component 14 is moved posterior relativeto what is currently available. This change alone, with somecurrently-available femoral components, will increase the amount offlexion achieved when compared to a standard tibial component.Additionally, in some such embodiments, the overall shape of the lateraltibial articular surface is modified. While such modification can beused for any suitable purpose, in some embodiments, the lateral tibialarticular surface is modified to allow the proximal tibia, when the kneeis flexed beyond approximately 120-130 degrees, to be positionedanteriorly enough so that there is no impingement of the posterior edgeor portion of the medial tibial articular surface on the proximalportion of the medial condyle of the femur. Therefore, greater deep kneeflexion may be achieved. It can thus be appreciated that the use of anembodiment of the above tibial component with a conventional femoralcomponent will facilitate greater flexion than will the use of aconventional tibial component. Similarly, the use of any of theabove-described femoral components with a conventional tibial componentwill facilitate more flexion than will use of a conventional tibialcomponent with a standard femoral component.

One having skill in the art will appreciate that the knee may (asdiscussed above) include at least one of a lateral pivot and a medialpivot. Accordingly, the embodiments of the present invention will beunderstood to be compatible with either or both of the lateral andmedial knee pivot configurations. In other words, while severalembodiments described above discuss the lateral tibial articular surface24 and the medial tibial articular surface 26 as having specificcharacteristics, in some embodiments, the placement of one or more ofthe aforementioned characteristics of the lateral tibial articularsurface and the medial tibial articular surface are reversed. In thisregard, the placement of each of the characteristics discussed above canbe reversed in any suitable manner that allows the lateral tibialarticular surface (or lateral tibial condylar surface) to comprise afixed center of rotation and that allows the medial tibial articularsurface (or medial tibial condylar surface) to allow the medial femoralcondyle to move anteriorly and posteriorly on a medial tibial plateau ofthe tibial component 14. By way of non-limiting illustration, in someinstances, FIGS. 6C and 6J illustrate portions of various tibialcomponents 14 comprising a lateral tibial condylar surface (e.g.,surface 26), while FIGS. 6D and 6K illustrate portions of various tibialcomponents 14 that include the medial tibial condylar surface (e.g.,surface 24).

In some embodiments of the present invention, greater deep knee flexionmay be provided or improved by modifying tibial articulation, in whichthe articulated surface of the tibial component is modified to encourageor limit articulation of the femoral component relative to the tibialcomponent. Examples of such modification are shown in FIGS. 6E-6I.

Referring now to FIGS. 6E, 6F, and 6I, a tibial component 14 is shown inaccordance with a representative embodiment of the present invention. Insome embodiments, the medial tibial condylar surface 26 of the tibialcomponent 14 is modified to include an articulation feature. Anarticulation feature is generally provided to compatibly interact withan opposing articulation surface of the femoral component. Duringflexion of the knee, the articulation surface of the femoral componentinteracts with the articulation feature of the medial tibial condylarsurface to guide or direct the articular movement of the femoralcomponent relative to the tibial component. Thus, in some embodiments,an articulation feature is provided to control articulation of the kneeduring deep flexion.

Various types of articulation features may be used in accordance withthe teaching of the present invention. For example, some embodiments ofthe articulation feature comprise an angled articular ridge 400. Thearticular ridge 400 is provided to compatibly interact with an opposingarticular surface of the femoral component. The interaction between thearticular ridge 400 and the articular surface of the femoral componentaffects a change in the articular movement of the femoral componentduring deep flexion of the knee. Indeed, in some embodiments, aninteraction between the femoral component and the articular ridge 400causes the posterior articulation of femoral component to shift whendeep flexion is achieved. Additionally, in some embodiments, thearticulation feature acts as the tibial full flex articulation.

The articular ridge 400 is generally disposed on the posterior surfaceof the tibial component 14 in a general medial-lateral direction 450.While the articular ridge can generally be disposed at any suitableangle with respect to an anteroposterior direction 460 of theintercondylar surface 28, in some embodiments, the articular ridge 400is disposed or positioned on the posterior surface at an angle θ that isobtuse to an anteroposterior direction 460 of the intercondylar surface28. In other embodiments, however, the articular ridge 400 is disposedor positioned on the posterior surface at an angle θ that is acute to ananteroposterior direction 460 of the intercondylar surface 28.Generally, angle θ of the articular ridge 400 is selected so as toachieve a desired articular shift of the femoral component during deepflexion. In some embodiments, an angle θ of approximately 0° toapproximately 110° is selected. In some other embodiments, an angle θ ofapproximately 0° to approximately 90° is selected. In yet otherembodiments, an angle θ of approximately 10° to approximately 45° isselected. Additionally, in some embodiments, an angle θ of approximately20° to approximately 35° is preferred. In still other embodiments, theangle θ falls in any suitable sub-range of the aforementioned ranges. Byway of illustration, FIG. 6E illustrates an embodiment in which thearticular ridge 400 runs at an acute angle to the anteroposteriordirection 460 of the intercondylar surface 28. Additionally, FIG. 6Iillustrates an embodiment in which the articular ridge 400 runssubstantially perpendicular to the anteroposterior direction 460 of theintercondylar surface 28.

The articular ridge 400 can have any suitable shape that allows thetibial component 14 to articulate against an articular surface of afemur and/or femoral component 12. Indeed, while some embodiments of thearticular ridge are substantially straight along their length, in otherembodiments, the articular ridge comprises an elongated ridge that isslightly bowed (as shown in FIG. 6E), that is curved along a portion ofits length, that follows a contour of a posterior edge of the lateralarticular surface 24, that follows a contour of a posterior edge of themedial articular surface 26 (as shown in FIG. 6I), that has a bentportion, and/or that is otherwise shaped to causes the posteriorarticulation of the femoral component to shift on the tibial componentwhen deep flexion is achieved.

The articular ridge 400 may be positioned anywhere on the articularsurface of the tibial component 14 so as to achieve a desired articularshift of the femoral component during deep flexion of the knee. Forexample, in some embodiments, the lateral tibial condylar surface 24 ismodified to include the articular ridge (not shown). In this example,any suitable amount of the articular ridge (or another articulationfeature) can be disposed within the lateral half (or completely withinthe lateral condylar surface) of the tibial component 14. Indeed, insome embodiments, the articular ridge (or other articulation feature) isdisposed at the lateral half (e.g., lateral to a central axis of theintercondylar surface 28) and does not extend into the medial half ofthe tibial component (at least not as a single continuous articularridge).

In other embodiments, the medial tibial condylar surface 26 includes thearticulation feature. In such embodiments, any suitable amount of thearticular ridge (or another articulation feature) can be disposed withinthe medial half (or completely within the medial condylar surface) ofthe tibial component 14. Indeed, in some embodiments, the articularridge (or other articulation feature) is disposed at the medial half(e.g., medial to a central axis of the intercondylar surface 28) anddoes not extend into the lateral half of the tibial component (at leastnot as a single continuous articular ridge). By way of illustration,FIG. 6E shows a representative embodiment in which the articular ridge400 is disposed completely within the medial condylar surface 26.

In still other embodiments, both the medial and lateral tibial condylarsurfaces 26 and 24 include an articular ridge 400 (or other articulationfeature). Although in some such embodiments, a single articular ridgespans between both the lateral and the medial condylar surfaces, inother embodiments, the lateral and the medial condylar surfaces eachcomprise a separate articular ridge (and/or other articulation feature).

In some embodiments, the articulation feature comprises a polyethylenecoating or layer. In other embodiments, the polyethylene coating isstrictly applied to the articular ridge 400 and precluded from extendingbeyond articular ridge 400 so as to impinge on the femur during flexion.

Referring now to FIGS. 6G and 6H, a tibial component 14 is shown inaccordance with a representative embodiment of the present invention. Insome embodiments, the medial tibial condylar surface 26 of the tibialcomponent 14 is further modified to include an articulation featurecomprising a spherical articular surface 420. The spherical articularsurface 420 is provided to compatibly interact with an opposingarticular surface of the femoral component. In some embodiments, theinteraction between the spherical articular surface 420 and thearticular surface of the femoral component enables unrestricted,natural, articular movement of the femoral component during deep flexionof the knee. In some embodiments, an interaction between the femoralcomponent and the spherical articular surface 420 permits a naturalposterior articulation of the femoral component when deep flexion isachieved. One of ordinary skill in the art will appreciate that thetibial component 14 may also be modified to permit femoral articulationon the lateral tibial condylar surface of the tibial component.Additionally, one of ordinary skill in the art will appreciate that thetibial component 14 may be modified to permit concomitant femoralarticulation on both the medial and lateral tibial condylar surfaces ofthe tibial component, for desired applications.

The spherical articular surface 420 may comprise a true spherical shape,or may comprise any other suitable shape, including, without limitation,a parabolic shape; a protuberance; a convex shape; a rounded, raisedbump; a raised, polygonal shape; a raised elliptical shape; a raisedirregular shape; and/or any other suitable shape that projects from anarticular surface of the tibial component (and/or tibia). One of skillin the art will appreciate that variations in the surface structure ofthe articular surface 420 may be required to provide an articularsurface that is optimally configured for a specific application or use.

The spherical articular surface 420 may be positioned anywhere on thearticular surface of the tibial component so as to achieve a desirednatural movement to the femoral component during deep flexion of theknee. Indeed, in some embodiments, the lateral tibial condylar surface24 is modified to include the spherical articular surface (not shown).In such embodiments, any suitable amount of the spherical articularsurface can be disposed within the lateral half (or completely withinthe lateral condylar surface) of the tibial component 14. Indeed, insome embodiments, the spherical articular surface is disposed at thelateral half (e.g., lateral to a central axis of the intercondylarsurface 28) and does not extend into the medial half of the tibialcomponent (at least not as a single, continuous spherical articulationsurface).

In other embodiments, the medial tibial condylar surface 26 includes thespherical articular surface (or articulation feature). In suchembodiments, any suitable amount of the spherical articular surface canbe disposed within the medial half (or completely within the medialcondylar surface) of the tibial component 14. Indeed, in someembodiments, the spherical articular surface is disposed at the medialhalf (e.g., medial to a central axis of the intercondylar surface 28)and does not extend into the lateral half of the tibial component (atleast not as a single continuous articular ridge). By way ofillustration, FIG. 6G shows a representative embodiment in which thespherical articular surface 420 is disposed completely within the medialcondylar surface 26.

In other embodiments, both the medial and lateral tibial condylarsurfaces 26 and 24 include a spherical articular surface 420. Althoughin some such embodiments, a single spherical articular surface spansbetween both the lateral 24 and the medial 26 condylar surfaces, inother embodiments, the lateral and the medial condylar surfaces eachcomprise a separate spherical articular surface (and/or otherarticulation feature).

In some embodiments, the articulation feature comprises a polyethylenecoating or layer. In other embodiments, the polyethylene coating isstrictly applied to the spherical articular surface 420 and precludedfrom extending beyond spherical articular surface 420 so as to impingeon the femur during flexion.

Additionally, while the articulation feature (e.g., articular ridge 400,spherical articular surface 420, etc.) is disposed at posteriorly on thetibial component 14 (and/or on a tibial articular surface), thearticulation feature can be disposed in any suitable location withrespect to the posterior edge of the tibial component (and/or tibialarticular surface). Indeed, while in some embodiments, the articularfeature is disposed at and/or extends to the posterior edge of thetibial component, in some other embodiments, the articular featureterminates (or lowers in elevation) anterior to the posterior edge.Indeed, (as shown in FIGS. 6G, 6E, and 6F) in some embodiments, asubstantially flat, concave, and/or raised articulation surface 416 isdisposed between a posterior portion of the articulation feature (e.g.,spherical articular surface 400 and/or spherical articular surface 420)and the posterior edge of the tibial component 14.

Where the tibial component 14 comprises a unicompartmental component,the articulation feature (e.g., the articular ridge 400, sphericalarticular surface 420, etc.) can be disposed in any suitable location onthe unicompartmental component. Indeed, while in some embodiments, thearticulation feature is simply disposed within the confines of theunicompartmental component (e.g., the lateral or medial unicompartmentalcomponent), in other embodiments, the articulation feature is disposedwithin the articular surface (e.g., the medial tibial condylar surface26 or the lateral tibial condylar surface 24) of the unicompartmentalcomponent.

In some embodiments, the opposing surface of the femur and/or femoralcomponent is modified to comprise a concave surface (not shown)configured to compatibly interface with the convex, spherical articularsurface 420 of the tibial component. In other embodiments, the opposingsurface of the femur and/or femoral component is modified to include aconcave groove (not shown) configured to compatibly interface with theconvex, articular ridge 400 of the tibial component. Further, in someembodiments the tibial component comprises a concave surface (not shown)and the femoral component comprises a convex surface (not shown) tocompatibly interact with the tibial concave surface. Still further, insome embodiments the polyethylene coating (not shown) or the articularsurface of the tibial component is configured to compatibly interfacewith a desired structure, shape or feature of the opposing femoralsurface, thereby achieving normal knee function and movement throughoutthe knee's range of motion. For example, in some embodiments a tibialcomponent is provided without an elevated, posterior portion orarticulation feature. Rather, the surgeon may elect to leave theposterior portion of the patient's tibia which in turn interfaces withthe femoral component to achieve normal knee function. Thus, in someembodiments a unicompartmental tibial component is provided to achievenormal knee function.

FIGS. 7A and 7B depict modifications to the femoral component 12 and thetibial component 14 to enable deeper knee flexion. Specifically, FIG. 7Adepicts a sagittal sectional view of a knee prosthesis 10 with amodified femoral component 12 and tibial component 14. In FIG. 7A anarea 102 of the femoral component 12 is removed, as represented by thedashed line. This area 102 is above and between the posterior extreme104 and the anterior side 106 of the posterior extreme 104. By removingthe area 102, deeper flexion for prosthetic knee patients is partiallyachievable.

Similarly, with the tibial component 14 in FIG. 7B, a medial side 25 mayappear to be relatively lengthened in the anteroposterior dimensionanteriorly by moving the articular surface 24 posterior and therebyhaving more of the tibial component anterior to theposteriorly-displaced medial articulation. This may give the appearanceof having removed a posterior portion of the tibial component 14 andmoved it to the anterior. A lateral side 27 of the tibial component maybe shortened in the anteroposterior dimension relative to the medialside 25 (i.e., area 100). FIG. 7B illustrates the foregoing in planview. In other words, by posteriorly shortening the lateral side 27(i.e., by removing area 100) of the tibial component 14 and bydisplacing the medial articular surface 24 more posterior, deeper kneeflexion is possible. And, these modifications create the opportunity fora prosthetic knee patient to achieve a deeper knee flexion than possiblewith currently-available prosthetic knees.

In at least some embodiments of the invention, greater deep knee flexioncan be achieved by providing an asymmetrical femoral component 12. Theasymmetrical femoral component 12 permits transfer of more than one-halfof the force transmitted across the joint to be transmitted to themedial side, as occurs in the normal knee. Some such embodiments areillustrated with reference to FIGS. 17 and 18A. FIG. 17 illustrates adrawing from a radiograph of a knee at about 160-degree flexion. In theradiograph, the femur 32 is viewed in the anteroposterior direction, anda medial condyle 66 of the femur 32, a lateral condyle 68 of the femur32, and a patella 70 are visible. As may be appreciated by reference tothe Figure, the medial-lateral width of the articulating portion of themedial condyle 66 is larger than the medial-lateral width of the lateralcondyle 68. Specifically, in the Figure, the medial-lateral width of thearticular portion of the medial condyle 66 is represented by X. As maybe seen in the Figure, in some embodiments, the medial-lateral width ofthe lateral condyle 68 is approximately 75% (or any suitable amountless) of the medial-lateral width X of the medial condyle 66. Indeed, insome embodiments, the medial-lateral width of the lateral condyle 68 isany suitable amount between about 10% and about 75% of themedial-lateral width X of the medial condyle 66. In still otherembodiments, the medial-lateral width of the lateral condyle 68 is anysuitable amount between about 30% and about 74% of the medial-lateralwidth X of the medial condyle 66. In yet other embodiments, themedial-lateral width of the lateral condyle 68 is any suitable amountbetween about 40% and about 70% of the medial-lateral width X of themedial condyle 66.

As may also be appreciated by reference to FIG. 17, the center of thepatella 70 is lateral to the midline of the knee. Specifically, in theFigure the medial-lateral distance between the most medial portion ofthe distal end of the femur 32 and the center of the patella 70 isrepresented by Y. As may be seen, the corresponding medial-lateraldistance between the most lateral portion of the distal end of the femur32 and the center of the patella 70 is approximately 75% or less (73% inthe Figure) of Y. In some embodiments of the invention, the femoralcomponent 12 may mimic the actual physical structure of the kneerepresented in FIG. 17.

In such embodiments of the femoral component as illustrated in FIG. 18A,the articular portion of the lateral condyle is, in its medial-lateralwidth, 75% or less than the width of the medial condyle. This allows formore than one half of the force that is transmitted across the joint tobe transmitted to the medial side, which is what occurs in the normalknee. It also allows the patellar or trochlear groove to be lateralizedbecause this groove distally is defined by its position between themedial and lateral condyles. In the normal knee the patella tends to beslightly lateralized on the femur and this lateral displacement of thegroove accomplishes what many conventional total knee replacementsaccomplish by externally rotating the femoral component 12 in the totalknee replacement. In one embodiment the condyles in the frontal planeare seen to be circular with a constant radius. The medial and lateralcondyles do not need to be the same radius, but may both be circularwhen viewed in that plane. When viewed in the sagittal plane thecondyles will be seen to have a closing radius posteriorly andanteriorly may blend into the anterior flange in the embodiments wherean anterior flange is used.

FIG. 18A illustrates a front view of one embodiment of a femoralcomponent 12 in accordance with the described embodiments. In theFigure, illustrative measurements are illustrated to show features ofthe described embodiment, and are not meant to be limiting of thefeatures of the described embodiments. As shown in FIG. 18A, the totalmedial-lateral width of the femoral component 12 may be approximately 72millimeters (mm). In this embodiment, the medial-lateral width of themedial femoral condylar surface 20 in the posterior portion of themedial posterior condyle is approximately 32 mm, while themedial-lateral width of the lateral femoral condylar surface 22 isapproximately 22 mm. Thus, in the illustrated embodiment, themedial-lateral width of the lateral femoral condylar surface 22 isapproximately 69% of the medial-lateral width of the medial femoralcondylar surface 20.

In the illustrated embodiment, a patellar groove 72 is defined by thespace between the medial femoral condylar surface 20 and the lateralfemoral condylar surface 22. Because the medial-lateral width of themedial femoral condylar surface 20 is larger than the medial-lateralwidth of the lateral femoral condylar surface 22, the patellar groove 72is displaced laterally, which is what occurs in the normal knee. As maybe appreciated by reference to FIGS. 18A through 18C, the patellargroove 72 may be provided at an angle as the patellar groove 72 movesfrom a most proximal anterior portion to a distal anterior portion to adistal posterior portion and to a proximal posterior portion. Forexample, the angle of the patellar groove 72 in FIG. 18A, as measuredfrom a sagittal plane is approximately 86 degrees. In other embodiments,however, the angle of the patellar groove can be any suitable angle thatis less than about 90 degrees and about greater than about 15 degrees(or any sub-range thereof). Indeed, in some embodiments, the patellargroove extends laterally from a distal anterior portion of the femoralcomponent to proximal-most, anterior portion of the femoral component atany suitable angle between about 40 degrees and about 89 degrees. Instill other embodiments, the patellar groove extends at any suitableangle between about 50 and about 85 degrees.

Thus, the illustrated embodiment shows how a femoral component 12 inaccordance with embodiments of the present invention may assist inachieving deeper knee flexion and, in some embodiments, full functionalflexion, by providing an asymmetric femoral component 12. The asymmetricfemoral component 12 may assist in achieving deeper knee flexion bybetter simulating physiologic loading and patellar tracking. Theasymmetric femoral component 12 allows for more normal loading of thejoint with the medial side taking more of the load than the lateralside. Additionally, the asymmetrical femoral component 12 allows formore anatomically correct lateral tracking of the patella which maydecrease problems of patellar pain, subluxation, and dislocation. One ofskill in the art will readily recognize that in some embodiments thetibial component 14 may be modified to accommodate an asymmetric femoralcomponent 12.

As discussed herein, at least some embodiments of the present inventionembrace providing deeper knee flexion capabilities where the medialfemoral side stays relatively fixed and the lateral side glides forwardsand backwards. While some embodiments embrace a knee with a tibialcomponent that keeps the femoral component relatively fixed on themedial side and able to glide on the lateral side, other embodimentsembrace a knee that is relatively fixed on the lateral side and able toglide on the medial side. This, for example, would apply to the tibialcomponent.

Additionally, while the additional articular surface on the femoralcomponent could be medial, lateral or both, at least some embodiments ofthe present invention embrace its application to use the tibial andfemoral full flex articulations either medially, laterally, or both.

Referring now to FIGS. 18B and 18C, in some embodiments, an abbreviatedanterior flange 610 is provided to replace the trochlear surface orgroove 72. In some embodiments, articular cartilage and underlying boneis optionally removed, which is typically removed with the antero-distalchamfer cut. In some embodiments, anterior flange 610 is provided tocompensate for individual patient anatomy where the lateral portion ofthe anterior condyle on a conventional prosthesis extends or sits moreproud than the bony condyle of the knee 200. For these anatomies, theproud position of the conventional prosthesis tents or otherwiseseparates the lateral soft tissues which may result in decreased flexionand discomfort or pain. In some embodiments, anterior flange 610 isprovided without replacing anterior condyles 20 and 22 of the distalfemur 210, such as for use with a patient having severe patello-femoralarthritis that would not be adequately treated with the prosthesis shownin FIGS. 12A, 12B, 14 and 16Q through 16S. Providing only anteriorflange 610 may also provide relief with reduced cost and/or reducedevasiveness. In other embodiments, anterior flange 610 is provided inaddition to replacing the anterior condyles 20 and 22.

In some embodiments, the length of the abbreviated anterior flange 610is very short so as to only replace a portion of the trochlear surface72. In other embodiments, the length of anterior flange 610 is extendedto entirely replace trochlear surface 72. Further, in some embodimentsanterior flange 610 is extended distally between the distal condyles 20and 22 to a length approximately equal to flanges of currentlyavailable, non-abbreviated prostheses.

Referring now to FIG. 21 a perspective side view of a knee 200 is shown.In at least some of the embodiments of the present invention, greaterdeep knee flexion may be further provided, improved, or enhanced byremoving a portion of the popliteal surface 202 of the femur 210. Thepopliteal surface 202 may include bone proximal to the posteriorarticular surfaces of the medial condyle, the lateral condyle, or boththe medial and lateral condyles. Resection of the popliteal surface 202may be accomplished by any appropriate method known in the art. Forexample, in one embodiment a portion of the tibia is first resectionedthereby providing sufficient clearance to resect the necessary portionof the popliteal surface 230.

The amount of bone resected from the tibia, the femur or both will varyfrom individual to individual depending upon the specific anatomy of thetibia and the femur. The resectioned popliteal surface 230 providesadditional clearance between opposing surfaces of the tibia 220 and thefemur 210. Specifically, the resectioned popliteal surface 230 preventsan impingement of the posterior articulate surface 250 of the medialcondyle 240 of the tibia 220 on the femur 210 during deep flexion of theknee 200. As such, the knee 200 may flex freely without the tibia 220adversely binding on, or contacting any portion of the femur 210.Additionally, the resectioned popliteal surface 230 may provide flexionexceeding 140°. In one embodiment, the resectioned popliteal surface 230provides flexion exceeding 160°.

Referring now to FIG. 22, a perspective side view of a knee 200 is shownfollowing resection of the popliteal surface 202 to provide theresectioned surface 230. As previously discussed, resection of thepopliteal surface 230 may be accomplished by any appropriate methodknown in the art. However, in one embodiment a resection block 300 isutilized to guide a cutting device 310 in making the resection 230. Theresection block 300 is comprised of a metallic material, similar to themetallic materials previously discussed, and includes an outer surface312, an inner surface 314, and a slot 316. The outer surface 312 iscontoured and adapted to substantially overlap the lateral and medialcondyles of the femur 210 however, in some embodiments, the guide wouldcover only the medial or lateral condyle. The inner surface 314 includesa plurality of angled surfaces that mirror the resectioned and shapedsurfaces of the lateral and medial condyles of the femur 210. Thus, theinner surface 314 of the resection block 300 is adapted to compatiblyengage the resectioned surfaces 62, 64, and 366 of the femur 210. Theengaged resection block 300 and femur 210 are further secured via aplurality of fasteners 320, such as screws. This may not be necessary inall cases. The fasteners 320 are required only to firmly attach theguide to the femur. In some embodiments, the interaction between theguide and the femur is such that the guide is held firmly in placewithout fasteners. In another embodiment, the guide is held in place byany means to facilitate an accurate resection of the above mentionedarea of the femur.

The interaction between the resection block 300 inner surface 314 andthe resectioned surfaces 62, 64, and 366 of the femur 210 accuratelyaligns the slot 316 with the popliteal surface 202 of the femur 210. Theslot 316 generally comprises an external opening 330 and an internalopening 332. The external opening 330 comprises a first width that isslightly greater than the width 338 of the cutting device 310. As such,the external opening 330 is adapted to compatibly receive the cuttingdevice 310. The internal opening 332 is positioned exactly adjacent tothe popliteal surface 202 and comprises a second width that is greaterthan the first width and approximately equal to the desired width of thepopliteal resection 230. Thus, the walls 334 of the slot taper inwardlyfrom the second opening to the first opening thereby providing a wedgedslot 316.

The cutting device 310 may include any device compatible with the slot316. In one embodiment an oscillating blade 340 is provided. Theoscillating blade 340 includes a shank 342, a cutting head 344 and astop 346. The shank 342 generally comprises a surface that is adapted tocompatibly and securely engage a tool (not shown) capable of moving theblade 340 relative to the resection block 300 and femur 210. The cuttinghead 344 generally comprises a plurality of teeth suitable for removingthe desired portions of the popliteal surface 202 to form the resection230. The stop 346 generally comprises a ferule, a crimp, or some otherfeature that provides a point on the blade 340 that is wider than thefirst opening 330 of the slot 316. As such, the stop 346 is unable toenter the slot 316 thereby limiting the depth into which the blade 340is permitted to enter the slot 316. Thus, the stop 346 acts as a depthgauge to control or limit the final depth of the popliteal resection230. In one embodiment, the stop 346 further comprises a set screwwhereby the stop 346 is loosened and repositioned on the blade 340 tochange the depth into which the blade 340 is permitted to enter the slot316. In another embodiment, the cutting device 310 is a burr bit havinga stop 346 to limit the cutting depth of the burr.

Referring now to FIG. 22A, an underside, perspective view of the femur210 and resection block 300 are shown. In one embodiment, the resectionblock 300 includes a first slot 316 and a second slot 318 separated by aconnecting portion 326 of the resection block 300. The first slot 316 ispositioned adjacent to the medial condyle 66 of the femur 210 and thesecond slot 318 is positioned adjacent to the lateral condyle 68. Eachslot is positioned at a different height relative to the asymmetric,natural positions of the medial and lateral condyles 66 and 68. Thus,the first and second slots 316 and 318 of the resection block 300 areadapted to optimally resect the popliteal surface 202 of the femur 210with respect to the asymmetric positions of the condyles 66 and 68. Inanother embodiment, the first and second slots 316 and 318 arepositioned at equal heights so as to provide a resectioned poplitealsurface 230 that is symmetrical without respect to the asymmetricalcondyles 66 and 68. In yet another embodiment, the positioning of theexternal opening 330 relative to the internal opening 332 of the firstslot 316 is different than the positioning of the external opening 330relative to the internal opening 332 of the second slot 318. As such,the radius of each wedge opening 316 and 318 is different and theresultant contours or shapes of the resectioned popliteal surface 230for the first and second slots 316 and 318 will be asymmetrical. Inanother embodiment, connecting portion 326 is eliminated therebyproviding a single guide slot. In this embodiment, upper and lowerportions of the guide are held in place relative to one another vialateral and medial bridges. The lateral and medial bridges maintain theposition of the upper and lower portions of the guide, as well as definethe outer edges of the slot. In another embodiment, lateral and medialbridges are used to provide multiple slots within the guide.

Referring now to FIGS. 22 and 22A, the popliteal resection 230 is madeby inserting the cutting device 310 into the slot 316 and removing thepopliteal surface 202 to the desired depth, as limited by the stopfeature 346 and the radial limitations of the wedged slot 316. Thewedged shape of the slot 316 permits the cutting device 310 to bepivoted along the radius of the wedge, wherein the contact between thestop 346 and the external opening 330 acts as a fulcrum for the radiusof the wedge. The resultant resection 230 therefore comprises a radialsurface configured and shaped to receive the femoral component 12 of theknee prosthesis. Following formation of the popliteal resection 230, thescrews 320, or other stabilizing methods, and the resection block 300are removed from the femur 210.

Referring now to FIGS. 23 and 23A, a cross-sectional side view of a knee200 is shown following resection of the popliteal surface 230. Thefemoral component 12 of the knee prosthesis may be modified tocorrespond to the resectioned portion 230 of the popliteal surface 202.For example, in one embodiment a portion 212 of the femoral component 12of the knee prosthesis is extended and contoured to seat within theresected portion 230 of the popliteal surface 202. As such, theposterior articular surface 250 of the medial plateau 240 of the tibia220 compatibly and smoothly interacts with the extended portion 212thereby further enabling the knee 200 to achieve deep flexion.Furthermore, the interaction between the posterior articulate surface250 and extended portion 212 prevents the posterior articulate surface250 from binding on a terminal surface 214 of the femoral component anddisplacing the femoral component 12 in an anterior direction during deepflexion. In some embodiments of the present invention, the extendedportion 212 is used in conjunction with a tibial implant having apartial spherical or convex medial side. In another embodiment, theextended portion 212 is used in conjunction with any knee replacementthat will allow knee flexion to 120° or greater. For example, in oneembodiment a femoral component of a knee prosthesis system is modifiedto include a piece of metal up the back of the posterior portion of thecomponent to provide an extended portion 212 compatible with the tibialcomponent of the knee prosthesis system.

In some embodiments of the present invention including the extendedportion 212, the femoral component 12 does not include an anteriorflange or any provision for patella-femoral articulation anteriorly, asshown in FIGS. 15B and 16B (and 12B) above. As such, the lack of ananterior flange allows the component 12 to be impacted onto the femur ina relatively conventional manner, except that, in some embodiments, thecomponent 12 is implanted after being rotated posteriorly relative to aconventional prosthesis. Additionally, the femoral component 12 can beused without a separate patella-femoral articular implant. In someembodiments, the component 12 is used with a modular flange attached tothe proximal end of the anterior oblique condyle of the condylar implantto provide an anterior femoral articulation for the patella to preventpatellar subluxation and to be used in cases of patella alta. In anotherembodiment, the femoral component 12 is used with separate, unattachedanterior patella-femoral implant articulations. In still otherembodiments, a separate femoral flange is used for a patella that doesnot have an implanted component. In yet other embodiments (as shown inFIG. 15E), the femoral component 12 comprises a truncated anteriorflange 213.

Where the femoral component 12 comprises a truncated anterior flange213, the truncated anterior flange can extend any suitable distance(e.g., to any suitable distance between about 0 and about 15 mm) oneither the proximal side or the distal side a proximal limit of thearticular cartilage, which is a physiological marker that would berecognized by one of skill in the art). Similarly, in some embodimentsin which the femoral component 12 comprises a truncated anterior flange213, the truncated anterior flange can extend proximally any suitableamount past an anterior proximal end 71 of the anterior oblique cut 64(and/or of the proximal limit of the articular cartridge) on a preparedfemur 32 (e.g., between about 0 mm and about 15 mm, between about 1 mmand about 10 mm, as little as between about 2 mm and about 5 mm, or anysuitable sub-range of the aforementioned distances).

In some embodiments, femoral component 12 further comprises a modularpatella-femoral component 57 (or a modular anterior flange), as shown inFIG. 16T. Modular patella-femoral component 57 is generally configuredto compatibly couple to femoral component 12 in an adjustable manner.For example, in some embodiments, modular patella-femoral component 57comprises a post 59 which is sized and configured to slidably insertwithin a groove or socket 13 of femoral component 12. The slidableinteraction between post 59 and socket 13 allows for infinite adjustmentof modular patella-femoral component 57 with respect to femoralcomponent 12, as shown in FIG. 16U.

The modular nature of femoral component 12 and patella-femoral component57 provides customized fitting of the prosthesis to the patient. Forexample, in some embodiments, a patella-femoral component 57 is selectedbased upon an anatomical need or feature of the patient. In otherembodiments, a femoral component 12 and a patella-femoral component 57are selected based upon a mechanical need for this feature for thepatient. Further, in some embodiments, a patella-femoral component 57 isselected to most accurately match a resectioned surface of the patient'sfemur. Accordingly, some embodiments of the present invention comprise aplurality of modular patella-femoral components 57 which areinterchangeably coupled with femoral component 12 as may be required ordesired to meet the needs of a patient.

The modular nature of femoral component 12 and patella-femoral component57 further facilitates the fitting process of the knee prosthesis. Forexample, in some embodiments a structural configuration of a unitaryfemoral component may preclude installation or may require thatadditional bone be resectioned from the patient's femur to permitinstallation. Accordingly, some embodiments of the present inventionprovide a method for fitting a patient with the knee prosthesis, whereinthe femoral component 12 of the knee prosthesis is initially fitted andsecured to a resectioned surface of a patient's femur. The modularpatella-femoral component 57 is then coupled or otherwise attached tothe femoral component 12 and adjusted 61 to accommodate the specificanatomy of the patient. Once the position of modular patella-femoralcomponent 57 is optimized, component 57 is secured to the patient'sfemur.

Referring now to FIG. 16V, a detailed view of an embodiment of socket 13of femoral component 12 and post 59 of modular patella-femoral component57 is shown. In some embodiments, socket 13 further comprises a taperedopening. Tapered opening 63 permits upward and downward adjustments 65of modular patella-femoral component 57 relative to a fixed position offemoral component 12. In some embodiments, tapered opening 63 furtherpermits lateral adjustments 67 of modular patella-femoral component 57relative to a fixed position of femoral component 12. Thus, taperedopening 63 provides infinite adjustment of modular patella-femoralcomponent 57 with respect to a fixed position of modular component 12.Further, in some embodiments, post 59 is tapered (not shown) therebyproviding additional adjustment of modular patella-femoral component 57with respect to femoral component 12, as may be desired.

In addition to the illustrated embodiments discussed above, thepatella-femoral component 57 and the femoral component 12 can bemodified in any suitable manner that allows the two components to beaffixed to a femur 32. Indeed, in some embodiments, instead of includinga post and socket coupling, the two components are coupled to each otherthrough any other suitable manner, including, without limitation,through the use of a butt joint, a lap joint, a butt-lap joint, arebated joint, a mortise and tenon, a dove-tail joint, a hinge, aflexible member, and any other suitable type of joint or combination ofjoints that allow the modular patella-femoral component 57 to be coupledto the femoral component 12.

In some embodiments, the patella-femoral component 57 and the femoralcomponent 12 are coupled by a butt joint. While such a butt joint canhave any suitable characteristic, in some embodiments, one of thecomponents (e.g., the patella-femoral component 57 or the femoralcomponent 12) comprises a convex surface, while the other (e.g., thefemoral component 12 or the patella-femoral component 57) respectivelycomprises a concave surface. By way of illustration, FIG. 16W shows arepresentative embodiment in which the femoral component 12 comprises aconvex surface 101 that couples with (i.e., abuts) a concave surface 103of the patella-femoral component 57. In such embodiments, the rotatableinteraction between the convex surface 101 and the concave surface 103allows for virtually infinite adjustment of the modular patella-femoralcomponent 57 with respect to the femoral component 12.

Where the patella-femoral component 57 and the femoral component 12 arecoupled by a butt joint (or any other suitable joint), the surfacesbetween the patella-femoral component 57 and the femoral component 12(e.g., the convex surface 101 and the concave surface 103) can have anysuitable characteristic that allows the two components to be connectedto each other. Indeed, while in some embodiments, the surfaces betweenthe two components are smooth, in other embodiments, such surfaces aretexturized to allow cement (or another adhesive) to bind tightly to thetwo components. While the surfaces between the components can betexturized in any suitable manner, in some embodiments, such surfacesare porous, roughened, knurled, comprise scaffolding, comprise ridges,comprise recesses, comprise protuberances, and/or are otherwisetexturized to hold cement (i.e., any other suitable adhesive) and/orbone growth.

Referring now to FIG. 23A, a cross-sectional side view of a knee 200 isshown following resection of the popliteal surface 230, wherein thefemoral component 12 is used in conjunction with a tibial component 14.In some embodiments of the present invention, the above describedfemoral component 12 is used in conjunction with a conventional tibialcomponent 14 that does not have the tibial full flex articulation. Forexample, in one embodiment the above described femoral component 12 isused in conjunction with a tibial component 14 that has the center ofthe medial tibial articulation displaced posteriorly. In anotherembodiment, the femoral component 12 is used in conjunction with atibial component 14 that has the center of the medial tibialarticulation in a position that corresponds with currently availabledesigns. In addition to occupying or lining the resectioned poplitealsurface 230, the extended portion 212 may include additional features tomodify the position of the tibia and the femur during full flexion.

For example, in one embodiment the extended portion 212 is modified torotate the tibia relative to the femur with the knee in full flexion. Inanother embodiment, the extended portion 212 is modified to preventrotation of the tibia relative to the femur with the knee in fullflexion. In yet another embodiment, the extended portion 212 is modifiedto include a spherical surface on its upper or most proximal portion. Assuch, this spherical surface allows the tibia to rotate relative to thefemur in full flexion. In some implementations of the present inventionit may be desirable to have the spherical surface articulate with acorresponding concave surface in the femoral full flex articulation.Such a concavity would offer medial-lateral stability, provide areacontact between the femoral and tibial components, and decreasepolyethylene wear of the prosthesis. Referring again to FIG. 23, in someimplementations of the present invention, the femoral component 12 isused in conjunction with a non-resected posterior portion of thepatient's own tibial plateau to articulate with extended portion 212.

Referring now to FIGS. 24 through 28, some embodiments of tibialcomponent 14 are further modified to include a stem 500 generallyattached to the anterior undersurface of tibial component 14. As shownin FIG. 24, anterior placement of stem 500 is calculated to compensatefor and decrease the compressive load applied to the posterior tibiaduring flexion of the knee joint. In some embodiments, as compressiveload is applied to the posterior tibia, stem 500 forms an interface withthe inner surface 520 of the tibial anterior cortex 518 therebypreventing at least one of rotation, sinking, and/or subsidence oftibial component 14 relative to the tibia 220. Thus, the shape, size,angle, and placement of stem 500 are selected to achieve a desiredinterface between the stem 500 and inner surface 520.

In some embodiments, stem 500 is curved or otherwise shaped to closelyapproximate the contours of a portion of inner surface 520, as shown inFIGS. 24 and 25. In other embodiments, stem 500 is tapered such thatportions of the stem surface contact various portions or areas of innersurface 520, as shown in FIG. 26. Still, in other embodiments, stem 500is extended such that a tip portion 530 of stem 500 contacts innersurface 520. Stem 500 may further include tapered fins 540 to increasethe stability of stem 500 while under compressive loads. In still someother embodiments, stem 500 comprises an adjustable linkage 550 wherebythe angle of stem 500 is adjusted to accommodate the individual anatomyof the patient, as shown in FIG. 28A. In some embodiments, stem 500further includes an adjustable tip 560 whereby the length of stem 500 isadjusted to accommodate the individual anatomy of the patient. Forexample, in some embodiments tip 560 is adjustably coupled to shaft 570via a set of threads 580. In other embodiments, tip 560 is slidablycoupled to shaft 570 wherein the position of the tip 560 relative to theshaft 570 is maintained via a set screw, a mechanical impingement, or anadhesive (not shown).

Thus, stem 500 may generally comprise any shape, size, length, or anglenecessary to accommodate the needs of the patient. Additionally, stem500 can comprise any suitable material. Indeed, in some embodiments,stem 500 is metal. In other embodiments, stem 500 is fabricated from aplastic, wherein the plastic stem may be trimmed at the time of surgeryto allow an optimal fit.

In some embodiments, stem 500 comprises a modular stem that isinterchangeable with one or more other stems of a varying size (e.g.,length, circumference, diameter, volume, etc.) and/or shape (e.g.,angle, curvature, taper, etc.). In this manner, a single tibialcomponent 14 can be modified such that its stem 500 is able to contactthe inner surface 520 of the tibial anterior cortex 518 of a variety oftibias having a different size and/or shape. For instance, in someembodiments in which the tibial component 14 is being placed on arelatively short tibia, a relatively short modular stem is attached tothe tibial component such that a portion (e.g., a tip) of the stem isable to contact an inner surface of the bone's anterior cortex. Incontrast, in some embodiments in which the tibial component is beingattached to a relatively long tibia, a relatively long modular stem isattached to the tibial component.

Where stem 500 comprises a modular stem, the modular stem can connect tothe tibial component 14 in any suitable manner, including, withoutlimitation, through the use of one or more threaded connectors,frictional engagements, adhesives, fasteners (e.g., screws, bolts, pins,rivets, pawls, etc.), mechanical connectors, and/or other mechanismsthat allow one of a variety of stems to be connected to the tibialcomponent. By way of illustration, FIG. 28B shows a representativeembodiment in which the undersurface 590 of the tibial component 14(e.g., a tibial component comprising a polymer articulation surface 593and metal base 597) comprises a connector 599 (e.g., a socket) that isconfigured to frictionally engage with a modular stem 501 (e.g., viasplined member 505 that is sized and shaped to be inserted intoconnector 599, as seen on a replacement stem 510).

Where stem 500 comprises a modular stem (e.g., stem 501), the modularstem can be used in any suitable manner. Indeed, in some embodiments,one or more modular stems (or even trial stems, such as stems made froma disposable material, stems having a smaller diameter to reduceunnecessary damage to the medullary cavity, autoclavable stems, etc.)are coupled to and/or removed from undersurface 590 (e.g., connector599) until the proper sized and/or shaped stem is found. At that point,the desired stem is permanently connected to the tibial component (e.g.,via cement, one or more fasteners, mechanical engagements, etc.).

Where stem 500 comprises a modular stem (e.g., stem 501), the modularstems of various sizes and shapes can be sold in any suitable manner,including, without limitation, separately and/or in sets.

Additionally, where stem 500 comprises a modular stem (e.g., stem 501),the various modular stems can be configured to extend any suitabledistance from the undersurface 590 of the tibial component 14. In someembodiments, the modular stems (and/or some embodiments of thenon-modular stems) are configured to extend (when attached to theundersurface 590 of the tibial component 14) any suitable distancebetween about 1 cm and about 20 cm from undersurface 590. In otherembodiments, the modular stems are configured to extend between about 3and about 15 cm from the undersurface of the tibial component 14. Instill other embodiments, the modular stems are configured to extendbetween about 5 and about 10 cm from the undersurface of the tibialcomponent. In yet other embodiments, the modular stems are configured toextend to within any suitable sub-range of the aforementioned extensionlengths.

Where the tibial component 14 includes stem 500 (e.g., a modular stem ora permanent stem that is configured to contact the inner surface 520 ofthe tibia, or the tibial anterior cortex 518), the undersurface 590 ofthe tibial component can contact the tibia in any suitable manner.Indeed, while the undersurface of the tibial component can be contouredin any suitable manner, in some embodiments, the undersurface of thetibial component 14 is substantially flat (e.g., as shown in FIG. 24).

Additionally, where the undersurface 590 of the tibial component 14 issubstantially flat, the proximal end of the tibia can be cut at anysuitable angle, and the undersurface 590 of the tibial component canhave any suitable angle that allows it to attach to the tibia. In oneexample, the undersurface of the tibial component 14 is angled, and theproximal end of the tibia is cut such that the undersurface of thetibial component slopes (with respect to a longitudinal axis of thetibia) distally from the tibial component's posterior edge 595 towardsthe component's anterior edge 598 (see e.g., FIG. 24). In anotherexample, undersurface 590 is angled, and the proximal end of the tibiais cut, such that the undersurface of the tibial component slopes (withrespect to a longitudinal axis of the tibia) distally from thecomponent's anterior edge 598 to the component's posterior edge 595. Instill another example, the undersurface of the tibial component 14 isconfigured such that the undersurface runs substantially perpendicularto a longitudinal axis of the tibia 220.

In still other embodiments (not shown), the tibial component 14 lacks astem 500 altogether. In such embodiments (as well as in embodiments inwhich the tibial component 14 comprises a modular stem 501 or anon-modular stem), the tibial component can be attached to a tibia inany suitable manner, including, without limitation through the use ofcement (and/or another adhesive); one or more screws, bolts, pins, orother fasteners; any other suitable connection mechanism; and/or anysuitable combination thereof. In this regard, in some embodiments inwhich the tibial component lacks a stem, undersurface 590 of the tibialcomponent comprises one or more types of scaffolding, recesses,knurling, features (e.g., protuberances, holes, dovetailed grooves,etc.), and/or any other structures or surface characteristics thatallows cement (and/or bone) to attach securely to the undersurface ofthe tibial component.

In some embodiments, a femoral component 600 is provided having ananterior extension 602 that generally replaces a resectionedantero-proximal portion of the anterior condyles 610, as shown in FIG.29A. In some embodiments, the antero-proximal portion of the anteriorcondyles 610 is prepared by resecting the anterior condyle surface tothe proximal limit 612 of the articular cartilage. As such, essentiallyall of the anterior articular cartilage is removed from the resectedfemur 32. In other embodiments, however, the anterior condyle surface ofthe femur is resected to any distance within (or any sub-range of) about0 mm and about 15 mm on either the distal or the proximal side of theproximal limit 612 of the articular cartilage. In one non-limitingexample, the anterior condyle surface of the femur is resected tobetween about 1 mm and about 6 mm on either the distal or the proximalside of the proximal limit 612 on the articular cartilage. In anothernon-limiting embodiment, the anterior surface of the femur is resectedproximally to any suitable amount less than about 15 mm of the proximallimit 612 of the articular cartilage.

In some embodiments, the anterior articular cartilage is removed whileremoving little or no other bone anteriorly. In other words, in someembodiments, femoral component 600 replaces essentially all anteriorarticular cartilage, but little or no other bone anteriorly.Accordingly, in some embodiments, the only bone removed is sub-chondralbone next to the cartilage and any bone necessary to allow a componentto fit the distal end of the femur. Thus, in some embodiments, femoralcomponent 600 is able to terminate at (or adjacent to (e.g., withinabout 0 and about 15 mm (or any suitable sub-range thereof) on eitherthe distal or the proximal side of)) the proximal limit 612. Moreover,in some embodiments, a resected distal end of the femur 32 is fittedwith a femoral component 600 wherein patellar force against the femur(in extension) is substantially, if not completely, eliminated due tohaving replaced the anterior articular cartilage with which the patellanormally articulates. Accordingly, in some embodiments, the resectionedantero-proximal portion of the anterior condyles 610 is replaced with ananterior condylar extension 602 thereby providing a new surface 604against which the patient's patella may articulate.

As shown in FIG. 29A, in some embodiments, femoral component 600 lacksan anterior flange (as discussed above) such that the femoral componentsubstantially ends at or distally (e.g., within about 0 mm and about 15mm, or any sub-range thereof) the proximal limit 612.

In some embodiments, the new articular surface 604 provides asubstantially smooth transition between femoral component 600 and femur32 at (or near) proximal limit 612. Further, by removing only thearticular cartilage and the underlying sub-chondral and cancellous bonefrom femur 32, a smaller, less expensive femoral component 600 may beprovided, which also results in a less invasive implantation for thepatient. Moreover, by allowing more bone to be preserved anteriorly onthe femur, femoral component 600 may allow for faster, less complicatedpreparation of the femur than may be accomplished with some competingfemoral prosthesis.

In some embodiments, femoral preparation and implantation of femoralcomponent 600 is performed using surgical instruments common to standardknee systems and procedures. In other embodiments, standard surgicalinstruments are used to make all of the desired cuts to the distalfemur, however, in some embodiments, the standard anterior femoral cutis not made. The standard antero-distal femoral cutting guide with mostsystems is typically adequate to remove essentially all anteriorcartilage to the proximal limit 612. Accordingly, there is nosignificant increase in instrument costs to implant femoral component600 as opposed to a standard femoral component.

Further, since the antero-distal condylar cuts to the femur 32 maycomprise standard cuts for fitting a standard femoral component, in someembodiments, a surgeon does not need to predetermine use of femoralcomponent 600 or a standard femoral component until they have completedall femoral cuts excepting the antero-distal cut, as this cut lies inroughly the same plane as the anterior femoral cortex. If the surgeondesires to implant femoral component 600, the surgeon cuts theantero-proximal portion of the posterior condyles 625 using anon-standard cutting guide. The standard antero-distal cut removesessentially all anterior cartilage to the proximal limit 612.Conversely, if the surgeon desires to implant a standard femoralcomponent, the surgeon makes the standard anterior cut necessary toaccommodate implantation of a standard femoral implant.

In one non-limiting example of a resected femur 32 suitable for use withfemoral component 600, FIG. 29A shows some embodiments in which femur 32is resected to include an anterior chamfer cut 622 (or anterior obliquecut, see FIG. 12C), a distal cut 623, a posterior chamfer cut 627, aposterior condylar cut 628, and a full flexion cut 624 (e.g., a cutextending proximally and anteriorly from the posterior condylar cut 628and/or towards a popliteal surface and/or posterior surface on the shaftof the femur).

The interior profile surfaces 620 of the femoral component 600 can bedesigned to match the interior profile of any conventional, standardfemoral component. In some embodiments, however, the interior profilesurfaces of opposing surfaces (e.g., internal surface 722, whichinterfaces with the anterior chamfer cut 622 and internal surface 724,which interfaces with the full flexion cut 624) of the femoral componentare exactly parallel or (in some cases) substantially parallel to allowa press-fit (including, without limitation, a cementless) or cementedapplication of femoral component 600 to resected surfaces (e.g., 622,623, 624, 627, and 628). In other embodiments, the interior profilesurfaces of the opposing surfaces (e.g., 722 and 724) diverge from eachother (or from being parallel with each other) by more than about 45°.In still other embodiments, however, the opposing surfaces (e.g., 722and 724) diverge by less than about 45°. Indeed, in some embodiments,the opposing surfaces diverge from each other by between about 0° andabout 45°. In still other embodiments, the opposing surfaces divergefrom each other by between about 3° and about 25°. In even otherembodiments, the opposing surfaces diverge from each other by betweenabout 5° and about 10°. In yet other embodiments, the opposing surfacesdiverge from each other by any suitable sub-range of any of theaforementioned ranges (e.g., between about 4° and about 8°).Additionally, while the opposing surfaces (e.g., 722 and 724) maydiverge in any suitable direction, in some embodiments, when femoralcomponent 600 is attached to a femur 32, the opposing surfaces (or atleast a portion of opposing surfaces) diverge from each other as thesurfaces run proximally.

Femoral component 600 can be attached to resected femur 32 in anysuitable manner. Indeed, while, in some embodiments, the femoralcomponent is configured to be rolled onto the femur, in otherembodiments, the femoral component is slid onto the femur withoutrolling. In the latter embodiments, the femoral component can be slidonto the femur in any suitable manner. In one non-limiting example,where the opposing surfaces (e.g., 722 and 724) diverge as they rundistally on a femur 32, the opposing surfaces are forced slightlyfurther apart to allow the component to be slid onto and press-fitted tothe femur. In this example, once the femoral component is in place, theopposing surfaces are allowed to return to the original position, whichcan help maintain the femoral component in place on the femur. Inanother example, where the opposing surfaces (e.g., 722 and 724) divergeas they run proximally on a femur 32 (e.g., giving the femur a slightlywedge-like characteristic), femoral component 600 is slid on andpress-fitted to the femur.

Where the femoral component 600 is slid onto the femur 32, the femoralcomponent can be slid on at any suitable angle relative to alongitudinal axis of the femur's shaft that allows the femoral componentto replace a desired portion of the femur's articulating surfaces. Insome embodiments, where the femoral component is slid onto the femur, itis slid at an angle θ (with respect to a longitudinal axis 626 of femur32, as shown in FIG. 29A) of between about 30° and about 55°. In otherembodiments, the femoral component is slid onto the femur at an anglebetween about 30° and about 45°. In yet other embodiments, femoralcomponent 600 is slid on the femur any angle that falls in any suitablecombination or sub-range of the aforementioned ranges of angles.

The femoral component 600 can be attached to the femur 32 in anysuitable manner, including through the use of cement (i.e., any suitableadhesive); one or more screws, pins, or other mechanical fasteners; apressure fitting (e.g., a friction fitting with or without cement);and/or any other known or novel method for attaching a prostheses to afemur. In some embodiments, however, the femoral component is simplycemented (as mentioned earlier) to the femur. In still otherembodiments, one or more surfaces of the femoral component 600 thatattach to the femur 32 comprise a texture (e.g., a porous texture,scaffolding, recesses, and/or other features) that allows bone to growinto the texturized surface.

The femoral component 600 can be modified in any suitable manner.Indeed, while in some embodiments, the femoral component is configuredto replace all of the articulating surfaces of a femur (e.g., in a fullfemoral knee replacement), in other embodiments, the femoral componentis configured to be used in a unicompartmental femoral knee replacement.Where the femoral component is used in a unicompartmental kneereplacement, the component can be used in any suitable location (e.g.,medially and/or laterally on the femur).

In another example of how the femoral component can be modified, in someembodiments, the femoral component comprises a full flex articulation 50(as discussed above and as shown in FIG. 29A). In another example,however, FIGS. 29B and 29C show that, in some embodiments, femoralcomponent 600 optionally lacks the full flex articulation. In thisexample, FIG. 29B shows that, in some such embodiments, a posteriorportion of the femur 32 can be removed so that the bone abuts andsubstantially corresponds with the shape of the proximal end 631 offemoral component 600. In contrast, FIG. 29C shows that, in someembodiments, either because of the natural shape of a patient's femur 32or because a surgeon removes a posterior portion of the femur 32 (asillustrated by the dashed line 634), the posterior portion of the femur32 does not abut with proximal end 631 of the posterior portion offemoral component 600.

In still another example, (discussed above) the full flexionarticulation 50 is added to femoral component 600 as a modular unit. Inyet another example, femoral component 600 replaces a popliteal surfaceof femur 32. In still another example, the femoral component isconfigured to receive a modular anterior flange 57 (as discussed above).

Thus, as discussed herein, the embodiments of the present inventionembrace knee prostheses. In particular, the present invention relates tosystems and methods for providing deeper knee flexion capabilities forknee prosthesis patients, more particularly, by effectuating one or moreof the following: (i) providing a greater articular surface area to thefemoral component of a knee prosthesis, with either a modification of,or an attachment to the femoral component of a knee prosthesis, whichwhen integrated with a patient's femur and an appropriate tibialcomponent, results in full functional flexion; (ii) providingmodifications to the internal geometry of the femoral component and theopposing femoral bone with methods of implanting; (iii) providingasymmetrical under surfaces on the tibial component of the kneeprosthesis and uniquely-positioned articular surfaces to facilitate fullfunctional flexion; (iv) asymmetrical femoral condylar surfaces with alateralized patellar (trochlear) groove to more closely replicatephysiologic loading of the knee and to provide better tracking of thepatella; and (v) resection of essentially all of the anterior femoralarticular cartilage and underlying bone, but no additional bone andreplacing it with a femoral component that does not have an anteriorflange as seen on contemporary prostheses.

The present invention may be embodied in other specific forms withoutdeparting from its spirit or essential characteristics. For example, oneof skill in the art will appreciate that the methods and systems of thepresent invention may be modified for use in unicompartmental kneearthroplasty procedures and prostheses. The methods and systems of thepresent invention may further be used on the lateral side of the kneeinstead of, or in combination with the medial side. Thus, the describedembodiments are to be considered in all respects only as illustrativeand not restrictive. The scope of the invention is, therefore, indicatedby the appended claims rather than by the foregoing description. Allchanges that come within the meaning and range of equivalency of theclaims are to be embraced within their scope.

What is claimed is:
 1. A tibial component, comprising: at least one of amedial tibial condylar surface and a lateral tibial condylar surface;and a first raised articulation feature disposed posteriorly on thetibial component, wherein a first articular surface disposed posteriorto a proximal-most portion of the first raised articulation feature isconfigured to articulate against a femoral component configured toreplace a distal portion of a femur.
 2. The tibial component of claim 1,wherein the first raised articulation feature is disposed at the medialtibial condylar surface.
 3. The tibial component of claim 2, wherein thefirst raised articulation feature is disposed at a posterior edge of themedial tibial condylar surface.
 4. The tibial component of claim 2,further comprising a second raised articulation feature comprising asecond articular surface that is disposed posterior to a proximal-mostportion of the second raised articulation feature, wherein the secondarticular surface is configured to articulated against the femoralcomponent, and wherein the second raised articulation feature isdisposed at a posterior edge of the lateral tibial condylar surface. 5.The tibial component of claim 1, further comprising a stem extendingfrom an undersurface of the tibial component, wherein a portion of thestein is configured to contact an inner, anterior surface of a tibiawhen the stem is inserted into the tibia and the undersurface of thetibial component is in contact with a resected surface of the tibia. 6.The tibial component of claim 1, wherein the first raised articulationfeature comprises a projection that projects from the at least one ofthe medial tibial condylar surface and the lateral tibial condylarsurface such that an articulation surface that is configured toarticulate with the femoral component is disposed posterior on thetibial component to the first raised articulation feature.
 7. The tibialcomponent of claim 1, further comprising the femoral component, whereina proximal portion of a posterior condyle of the femoral componentcomprises an incurvate articulation surface that is configured toarticulate with the first raised articulation feature when the tibialcomponent and the femoral component are seated in a knee joint and theknee joint is flexed.
 8. The tibial component of claim 1, wherein thefirst raised articulation feature comprises an articular ridge that runsin a general media-lateral direction.
 9. The tibial component of claim1, wherein a portion of the first raised articulation feature runs at anangle that is at least one of perpendicular to and acute to ananteroposterior direction of an intercondylar surface of the tibialcomponent.
 10. The tibial component of claim 1, wherein the first raisedarticulation feature comprises a spherical articular surface disposed ata medial portion of the tibial component.
 11. The tibial component ofclaim 1, wherein the medial tibial condylar surface comprises a concavearticulation surface having a fixed center of rotation with a lowestpoint disposed from a posterior edge of the tibial component by betweenabout 18% and about 35% of a total anteroposterior dimension of thetibial component, and wherein the lateral tibial condylar surfacecomprises a substantially flat articulation surface having a length thatextends in an anteroposterior direction.
 12. A tibial component,comprising: a medial tibial condylar surface; and a raised articulationfeature disposed posteriorly at the medial tibial condylar surface,wherein an articular surface disposed posterior to a proximal-mostportion of the raised articulation feature is configured to articulateagainst an articulation surface of a femoral component.
 13. The tibialcomponent of claim 12, wherein the raised articulation feature isdisposed at a posterior edge of the medial tibial condylar surface. 14.The tibial component of claim 12, further comprising the femoralcomponent, wherein a proximal portion of a posterior, medial condyle ofthe femoral component comprises an incurvate articulation surface thatis configured to articulate with the raised articulation feature whenthe tibial component and the femoral component are seated in a kneejoint and the knee joint is flexed.
 15. The tibial component of claim14, wherein the raised articulation feature is configured to function asa fulcrum for the femoral component.
 16. The tibial component of claim12, further comprising a stem extending from an undersurface of thetibial component, wherein a portion of the stem is configured to contactan inner, anterior surface of a tibia when the stem is inserted into thetibia and the undersurface of the tibial component is in contact with aresected surface of the tibia.
 17. A tibial component, comprising: amedial tibial condylar surface; a raised articulation feature disposedat a posterior edge of the medial tibial condylar surface; and a stemextending from an undersurface of the tibial component, wherein aportion of the stem is configured to contact an inner, anterior surfaceof a tibia when the stem is inserted into the tibia and the undersurfaceof the tibial component is in contact with a resected surface of thetibia, and wherein an articular surface disposed posterior to aproximal-most portion of the raised articulation feature is configuredto articulate against an articulation surface of a femoral component.18. The tibial component of claim 17, wherein the raised articulationfeature comprises an articular ridge that runs in a generalmedia-lateral direction on the tibial component and at an angle that isat least one of perpendicular to and acute to an anteroposteriordirection of an intercondylar surface of the tibial component.
 19. Thetibial component of claim 17, further comprising the femoral component,wherein a proximal portion of a posterior, medial condyle of the femoralcomponent comprises an incurvate articulation surface that is configuredto articulate with the raised articulation feature when the tibialcomponent and the femoral component are seated in a knee joint and theknee joint is flexed.
 20. The tibial component of claim 19, wherein theraised articulation feature is configured to function as a fulcrum forthe femoral component.